Method for patterning metal using nanopraticle containing percursors

ABSTRACT

Continous, conducting metal patterns can be formed from metal nanoparticle containing fils by exposure to radiation. The metal patterns can be one, two, or three dimensional and have high resolution resulting in feature sizes in the order of micron to nanometers

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to the patterning of a metalfeature using a metal nanoparticles containing material and exposing itto radiation.

[0003] 2. Discussion of the Background

[0004] Currently available technology for the micro fabrication of metalpatterns includes:

[0005] 1) use of masks to define patterns of metal by deposition oretching (Shacham-Dianiand, Y., Inberg, A., Sverdlov, Y. & Croitoru, N.,Electroless silver and silver with tungsten thin films formicroelectronics and microelectromechanical system applications. Journalof the Electrochemical Society, 147, 3345-3349 (2000));

[0006] 2) laser ablation of metal films to create patterns;

[0007] 3) laser direct writing based on pyrollitic deposition of metalfrom vapor, solution or solid precursors; (Auerbach, A., On DepositingConductors From Solution With a Laser, Journal of the ElectrochemicalSociety, 132, 130-132 (1985); Auerbach, A., Optical-Recording ByReducing a Metal Salt Complexed to a Polymer Host, Applied PhysicsLetters, 45, 939, 941 (1984); Auerbach, A., Copper Conductors ByReduction of Copper (I) Complex in a Host Polymer, Applied PhysicsLetters, 47, 669-671 (1985); Auerbach, A., Method For ReducingMetal-Salts Complexed in a Polymer Host With a Laser, Journal of theElectrochemical Society, 132, 1437-1440 (1985)); and

[0008] 4) light exposure and development of silver-halide basedphotographic film followed by electroless and electrochemical plating(Madou, M. & Florkey, J., From batch to continuous manufacturing ofmicrobiomedical devices. Chemical Reviews, 100, 2679-2691 (2000); M.Madou., Fundaments of Microfabrication (CRC Press, Boca Raton, 1997);Madou, M., Otagawa, T., Tierney, M. J., Joseph, J. & Oh, S. J.,Multilayer Ionic Devices Fabricated By Thin-Film and Thick-FilmTechnologies. Solid State Ionics, 53-6, 47-57 (1992)).

[0009] Currently available methods are described, for example, in thefollowing publications:

[0010] Southward, R. E. et al., Synthesis of surface-metallizedpolymeric films by in situ reduction of(4,4,4-trifluoro-1-(2-thienyl)-1,3-butanedionato) silver(I) in apolyimide matrix. Journal of Materials Research, 14, 2897-2904 (1999);

[0011] Southward, R. E. & Thompson, D. W. Inverse CVD, A novel syntheticapproach to metallized polymeric films. Advanced Materials, 11,1043-1047 (1999);

[0012] Gu, S., Atanasova, P., Hampden-Smith, M. J. & Kodas, T. T.,Chemical vapor deposition of copper-cobalt binary films. Thin SolidFilms, 340, 45-52 (1999);

[0013] Jain, S., Gu, S., Hampden-Smith, M. & Kodas, T. T., Synthesis ofcomposite films. Chemical Vapor Deposition, 4, 253-257 (1998);

[0014] Gu, S., Yao, X. B., Hampden-Smith, M. J. & Kodas, T. T.,Reactions of Cu(hfac)(2) and Co-2(CO)(8) during chemical vapordeposition of copper-cobalt films. Chemistry of Materials, 10, 2145-2151(1998);

[0015] Calvert, P. & Rieke, P., Biomimetic mineralization in and onpolymers. Chemistry of Materials, 8, 1715-1727((1996);

[0016] Hampden-Smith, M. J. & Kodas, T. T. Chemical-Vapor-Deposition ofMetals. 2. Overview of Selective CVD of Metals. Chemical VaporDeposition, 1, 3948 (1995),

[0017] Hampden-Smith, M. J. & Kodas, T. T., Chemical-Vapor-Deposition ofMetals. 1. an Overview of CVD Processes. Chemical Vapor Deposition, 1,8-23 (1995);

[0018] Xu, C. Y., Hampden-Smith, M. J. & Kodas, T. T., Aerosol-AssistedChemical-Vapor-Deposition (AACVD) of Binary Alloy (Ag(x)Pd(1)-X,Cu(x)Pd(1)-X, Ag(x)Cu(1)-X) Films and Studies of Their CompositionalVariation. Chemistry of Materials, 7, 1539-1546 (1995); and

[0019] Naik, M. B., Gill, W. N., Wentorf, R. H. & Reeves, R. R., CVD ofCopper Using Copper(I) and Copper(II) Beta-Diketonates. Thin SolidFilms, 262, 60-66 (1995).

[0020] The above described methods are limited to direct production oftwo-dimensional patterns, and three-dimensional patterns must be builtup by use of multilayer or multistep processes. Laser direct writing ofmetal lines allows for single step microfabrication of one-dimensionalor two-dimensional patterns, but has mainly involved thermaldecomposition of a metal precursor at a high temperature created byabsorption of laser energy. There is great interest in an ambienttemperature process for forming metal lines by laser writing and fordirectly writing three-dimensional metal patterns.

[0021] Swainson et al., in a series of patents, (U.S. Pat. No.4,466,080; U.S. Pat. No. 4,333,165; U.S. Pat. No. 4,238,840; and U.S.Pat. No. 4,288,861) described the photoreduction of silver by usingconventional dyes such as methylene-blue and others as silverphotoreducing agents in solution. Silver coatings of surfaces followingoptical excitation of such silver ion and dye solutions were described.The presence of “certain reducing/chelating agents, such aso-phenanthroline” were described as being a fundamental component of thesystem. Swainson also described that by following similar methods onewould not be able to write continuous metal phases within a solidmatrix. In fact, the introduction to the sections that included themetal photoreduction stated that the previously generally preferredstabilized or solid media are not suitable for the production ofproducts with a material complexity above a certain level. Accordingly,their examples used gaseous and liquid physical states which accordingto Swainson permit increased complexity of products by virtue of theirtransportive capability. In the solid state, the present inventors haveindeed found that Swainson's method does not result in the formation ofcontinuous metal.

[0022] Whitesides et al. described a multistep method for the generationof conductive metal features both in an article: Deng T., Arias, F.,Ismagilov, R. F., Kenis, P. J. A. & Whitesides, G. M., Fabrication ofmetallic microstructures using exposed, developed silver halide-basedphotographic film. Analytical Chemistry, 72, 645-651 (2000); and in U.S.Pat. No. 5,951,881. The key difference between the system described byWhitesides et al. and the system of the present invention is that theyphotochemically generate metal nanoparticles in a gelatin and in asubsequent step they use an electroless deposition of silver on thesilver crystals, so as to develop it (Braun, E., Eichen, Y., Sivan, U. &Ben-Yoseph, G., DNA-templated assembly and electrode attachment of aconducting silver wire. Nature, 391, 775-778 (1998)), thus forming acontinuous metal structure. Moreover, in order to obtain real 3Dpatterns they have to perform multi-step construction of the device. Thesmallest dimension of the lines (30 μm) described by Whitesides et al.is much larger than the one achievable with the method according to thepresent invention.

[0023] Reetz et al. described in an article and a patent titled:“Lithographic process using soluble or stabilized metal or bimetalclusters for production of nanostructures on surfaces” the fabricationvia electron beam irradiation of continuous metal features starting fromsurfactant stabilized metal nanoparticles (Reetz, M. T., Winter, M.,Dumpich, G., Lohau, J. & Friedrichowski, S. Fabrication of metallic andbimetallic nanostructures by electron beam induced metallization ofsurfactant stabilized Pd and Pd/Pt clusters. Journal of the AmericanChemical Society 119, 4539-4540 (1997); Dumpich, G., Lohau, J.,Wassermann, E. F., Winter, M. & Reetz, M. T. in Trends and NewApplications of Thin Films 413-415 (Transtec Publications Ltd,Zurich-Uetikon, 1998). Bedson et al., describe the electron beam writingof metal nanostructures starting from passivated gold clusters, thatwere alkylthiol capped gold nanoparticles. Bedson T. R, Nellist P. D.,Palmer R. E., Wilcoxon J. P. Direct Electron Beam Writing ofNanostructures Using Passivated Gold Clusters. MicroelectronicEngineering 53, 187-190 (2000)).

[0024] The differences between what is described there and the presentinvention are:

[0025] 1) Reetz et al's and Bedson et al's processes involve fusion ofnanoparticles rather than the growth of nanoparticles based on thegeneration of metal atoms upon excitation;

[0026] 2) their starting materials are made solely of stabilizednanoparticles, whereas we teach the use of composite materials in whichstabilized nanoparticles are just one of the components;

[0027] 3) their irradiation method is solely electron-beam irradiation,while we teach that using suitable reducing agents our compositematerials can be good precursors for a wide variety of stimulatingradiation, electron-beams being just one of them; and

[0028] 4) their nanoparticles are coated with ligands that provide onlystabilization solubilization properties, while our compositions forelectron beam patterning of metal are composites based on nanoparticles,metal salt, and an excited dye reducing agent, that can be included bycovalent attachment to a ligand on the nanoparticle.

[0029] The compositions and methods of excitation of dyes with strongmultiphoton absorption properties have been disclosed by Marder andPerry, U.S. Pat. No. 6,267,913 “Two-Photon or Higher-Order AbsorbingOptical Materials and Methods of Use”.

[0030] Some compositions and methods have been disclosed for themultiphoton generation of reactive species including the photogenerationof silver particles in a patent application by B. H. Cumpston, M.Lipson, S. R. Marder, J. W. Perry “Two-Photon or higher order absorbingoptical materials for generation of reactive species” U.S. patentapplication No. 60/082,128. The method taught in U.S. patent applicationNo. 60/082,128 differs from those of this invention because in the priorapplication there is no mention of the use of metallic nanoparticles asprecursors.

SUMMARY OF THE INVENTION

[0031] It is an object of the present invention to provide a processfor 1) direct fabrication of one, two or three-dimensionalmicrostructures of metal in a single processing step, and 2) thefabrication of nanometer scale metal patterns in one or two dimensionalpatterns also in a single processing step. Specifically, it is an objectof the present invention to provide a low temperature process forforming metal lines by laser writing and for directly writingthree-dimensional patterns.

[0032] These and other objects have been achieved by the presentinvention the first embodiment which includes a method for growth of apre-nucleated metal nanoparticle, comprising:

[0033] providing said pre-nucleated metal nanoparticle in a composite;

[0034] generating a metal atom by reducing a metal ion by exposure toradiation;

[0035] reacting said metal atom with said pre-nucleated metalnanoparticle, thereby growing a metal nanoparticle.

[0036] Another embodiment of the invention includes a method for growthof a pre-nucleated metal nanoparticle, comprising:

[0037] forming a film from said pre-nucleated metal nanoparticle, ametal salt, a dye and a polymer matrix;

[0038] generating a metal atom by reducing a metal ion of said metalsalt by exposure to radiation;

[0039] reacting said metal atom with said pre-nucleated metalnanoparticle, thereby growing a metal nanoparticle.

[0040] Yet another embodiment of the present invention includes a metalnanoparticle containing composition, comprising:

[0041] a ligand coated metal nanoparticle;

[0042] a dye;

[0043] a metal salt; and

[0044] optionally a sacrificial donor.

[0045] Another embodiment of the present invention includes a metalnanoparticle containing composition, comprising:

[0046] a ligand coated metal nanoparticle;

[0047] a dye;

[0048] a metal salt; and

[0049] a matrix.

[0050] A further embodiment of the present invention includes a method,comprising:

[0051] subjecting one of the above metal nanoparticles containingcompositions to radiation, thereby effecting a growth of saidnanoparticles; and

[0052] forming a continuous or semi-continuous metal phase.

[0053] The present invention further includes a method, comprising:

[0054] forming a film from a metal nanoparticle, a metal salt, a dye anda polymer matrix; and

[0055] exposing said film to radiation, thereby producing a pattern of aconductive metal.

BRIEF DESCRIPTION OF DRAWINGS

[0056]FIG. 1. Schematic illustration of case 1 growth process.

[0057]FIG. 2. Energy level scheme for sensitized metal ion reduction.

[0058]FIG. 3. Illustration of writings of metal features in ananoparticle composite.

[0059]FIG. 4. Optical transmission image, (top view) of a 3D structure(200×200×65 μm) written in a polymer matrix.

[0060]FIG. 5. Optical image of the same structure shown in FIG. 4 on alarger scale.

[0061]FIG. 6. SEM image of a 3D metallic silver microstructure formed bytwo-photon writing in a composite film.

[0062]FIG. 7. XPS spectrum and image of a set of silver lines.

[0063]FIG. 8. Schematic drawing of the attachment of a ligand cappedmetal-nanoparticle to a thiol functionalized glass substrate.

[0064]FIG. 9. TEM images illustrating growth of metal nanoparticle in acomposite film upon exposure to either one or three laser pulses from ans pulsed laser.

[0065]FIG. 10. Silver ribbon written with a two-photon irradiation.

[0066]FIG. 11. Silver lines written using a one-photon excitation.

[0067]FIG. 12. Optical micrograph of a copper square written bytwo-photon excitation.

[0068]FIG. 13. Spectrum of sample from control experiment.

[0069]FIG. 14. SEM picture of the corner of a 3D metallic silverstructure written using two-photon excitation.

[0070]FIG. 15. TEM image of chemically synthesized nanoparticles used asa precursor in the composites.

[0071]FIG. 16. Examples of a square and a line written and imaged usingan SEM.

[0072]FIG. 17. Laser and electron-beam induced growth of silvernanoparticles in a nanoparticle/salt composite.

[0073]FIG. 18. Transmission optical microscopy of a line written in aPVK film doped with AgBF₄ and nAg12.

[0074]FIG. 19. Reflection image of a silver square embedded in a polymernanocomposite.

[0075]FIG. 20. Schematic drawing of the slide/polymer/microfabricatedline configuration used to measure the conductivity of the grown wires.

[0076]FIG. 21. Plot of an I(V) curve.

[0077]FIG. 22. Metallic structures fabricated in nanocomposites bytwo-photon scanning laser exposure.

[0078]FIG. 23. Optical set ups for the writing and reading of holograms.

[0079]FIG. 24. Reconstructed holographic image.

DETAILED DESCRIPTION OF THE INVENTION

[0080] The present invention relates to the use of metal nanoparticlecontaining films in conjunction with exposure to radiation to activatethe growth and fusion of such particles to form continuous conductingmetal patterns. In the process, one, two, or three dimensional,continuous conducting metal wires or other patterns may be formed.

[0081] The novel metal nanoparticle systems and methods of exposure forthe direct patterning of metal in three dimensions and with highresolution in the order of microns to nanometers, are unprecedented.Subjecting certain nanoparticle containing compositions to forms ofexcitation can result in growth of these particles, leading ultimatelyto a continuous (or semi-continuous) metal phase. Patterned excitationleads to formation of corresponding metallic patterns. Methods based ontwo types of compositions and involving free space optical exposure,near-field optical exposure or exposure with ionizing radiation, such aselectrons from the conductive tip of an scanning probe microscope aredescribed herein.

[0082] In the process of the present invention, radiation from differentsources results in different resolution. For example, a feature sizes ofdown to 300 nm can be achieved using a blue laser and one photonexcitation. A feature size of down to 100 nm, and preferably down to 50nm may be achieved using a near field light source. If two photonexcitation is used, the feature size may be down to 100 nm, preferably50 nm. Electron-beams allow for a resolution of 10 nm to 300 nm. Focusedion beam allow for a feature size of down to 5 to 10 nm. An extremelysmall feature size of down to 5 nm may be achieved using a ScanningProbe Microscope tip.

[0083] The nanoparticles used in the method according to the presentinvention are mainly those coated with organic ligands. By ligand, wemean any molecule or ion that has at least one atom having a lone pairof electrons that can bond to a metal atom or ion. By ligand, we alsomean unsaturated molecules or ions that can bond to a metal atom or ion.Unsaturated molecules or ions possess at least one π-bond, which is abond formed by the side-by-side overlap of p-atomic orbitals on adjacentatoms. One example of an organic ligand for silver, gold, or coppernanoparticles is an n-alkylthiol ligand, which preferably has an alkylchain length of 4 to 30 carbons. The coatings of the nanoparticlesrender them soluble in common organic solvents and processable bysolution processing techniques. These coatings scan also stabilize thenanoparticle with respect to aggregation and/or coalescence of the metalcore of the particle. Throughout this disclosure, the term ligand coatednanoparticle is used to describe such stabilized particles. Furthermore,according to the present invention, nanoparticles with two or moredifferent types of ligands, such as two alkylthiol ligands of differentlengths exhibit increased solubility in organic solvents and polymermatrices, such as poly(vinyl carbazole) and a reduced tendency towardsthe formation of aggregates resulting from inter-digitation of ligands,compared to nanoparticles coated with one type of alkylthiol ligand,which are known to form aggregates with interdigitated ligands. Voicu,R., Badia, A., Morin, F., Lennox, R. B. & Ellis, T. H., Thermal behaviorof a self-assembled silver n-dodecanethiolate layered material monitoredby DSC, PTIR, and C-13 NMR spectroscopy. Chemistry of Materials, 12,2646-2652 (2000); Sandhyarani, N., Pradeep, T., Chakrabarti, J., Yousuf,M. & Sahu, H. K. Distinct liquid phase in metal-cluster superlatticesolids. Physical Review B, 62, 8739-8742 (2000); Sandhyarani, N. &Pradeep, T., Crystalline solids of alloy clusters. Chemistry ofMaterials, 12, 1755-1761 (2000); Badia, A. et al., Self-assembledmonolayers on gold nanoparticles. Chemistry-a European Journal, 2,359-363 (1996)). The use of nanoparticles with two or more types ofligands for the formation of a metal nanoparticle/polymer composite isadvantageous because a higher concentration of particles may be achievedand the optical quality of the composite may be higher, since thereduction of aggregation leads to lower optical scattering compared tocomposites including nanoparticles with a single type of alkylthiolligand. The ligand coated nanoparticles can be easily spin coated,casted or inserted as dopants into organic films or diffused intoinorganic glasses prepared via sol-gel chemistry. Two classes ofcompositions are described here. They differ in the nature of thematrix:

[0084] Class I is a composition in which the ligand coated nanoparticlesthemselves are the matrix.

[0085] Class II is a composition in which a polymer, a glass or a highlyviscous liquid is the matrix, and the nanoparticles are dopants.

[0086] It is known that photochemical reduction of metal ions, such assilver ions (Ag⁺), by suitable dye molecules leads to the formation ofAg⁰ atoms and the nucleation of small, nanometer-sized particles of Ag⁰.However, a key problem with past attempts to photochemically writecontinuous, conducting metal patterns is that the limited supply ofmetal ions in the precursor material, as well as the high degree ofexcitation required to provide nucleation centers makes the growth ofcontinuous metal quite difficult. Particles formed are typically notinterconnected and do not form a conductive path. With this type ofproduct one would have to perform an additional wet chemical processingstep to “develop” the particles to form conductive lines. However,according to the present invention, incorporation of ligand-coatedsilver nanoparticles into the precursor material overcomes this problemby providing both initial nucleation sites for growth of the metal, andsome starting volume fraction of metal. Upon sufficient growth, thesurface coverage of the ligand on the nanoparticle becomes insufficientto prevent the particle from undergoing fusion with other neighboringgrowing particles to form a larger metal phase. The surface coverage ofthe ligand on the nanoparticle becomes insufficient to prevent theparticle from undergoing fusion with other neighboring growing particlesto form a larger metal phase. Thus, upon sufficient growth thenanoparticles become highly interconnected and form well conductingpathways. The approach disclosed here allows for direct and simple,photochemical fabrication of microstructures of conductive metal, at lowtemperatures, such as ambient room temperature (21° C.).

[0087] One type of composition that is effective in the method accordingto the present invention involves a composite containing a) metalnanoparticles, b) a metal salt and c) a dye, capable of excited statereduction of the metal ions and possessing appropriate light absorptionproperties, and d) a polymer host material. Many variations on thecomposition of this composite are possible, including: 1) the type ofmetal nanoparticle, 2) the type of metal ion, 3) the counterion of themetal salt, 4) the structure of the dye, 5) whether or not a polymerhost is used, and 6) the type of polymer host if one is used. By theterm dye, we mean a molecule or ion that absorbs photons withwavelengths ranging from 300 nm to 1.5 μm. Depending on the composition,metal nanoparticle/polymer nano-composites with good light transmissionproperties and large thickness, up to hundreds of micrometers,preferably up to 500 micrometers, more preferably up to 700 micrometersand most preferably up to 900 micrometers, can be prepared. In themethod according to the present invention, such composite can be exposedin a patterned manner with optical radiation or with ionizing radiationbeams, either by use of a mask or by suitable scanning of a highlyconfined beam of radiation, to produce a pattern of conductive metal.

[0088] According to the present invention, compositions incorporatingdye molecules possessing two-photon absorption cross sections greaterthan or equal to 1×10⁻⁵⁰ cm⁴ photon⁻¹ sec⁻¹ and capable of excited-statereduction of the metal ions can be used to create three dimensionalpatterns of conductive metal. Examples of dye molecules with largetwo-photon absorption cross sections are described in U.S. Pat. No.6,267,913 which is included herein by reference. In the presentembodiment, a tightly focused, high intensity laser beam tuned to thetwo-photon absorption band of the dye is used to localize thephotoactivated growth of metal to a small volume. The ability to achievehigh 3D spatial resolution arises from the fact that the probability ofsimultaneous absorption of two photons depends quadratically on theintensity of the incident laser light. If a tightly focused beam isused, the intensity is highest at the focus and decreases quadraticallywith the distance (z) from the focal plane, for distances larger thanthe Rayleigh length. Thus, the rate at which molecules are exciteddecreases very rapidly (as z⁻⁴) with the distance from the focus and theexcitation is confined in a small volume around the focus (of the orderof λ³, where λ is the wavelength of the incident beam). The sample orthe focused beam can be scanned and the intensity controlled to map outa three dimensional pattern of exposure and to produce 3D structurescomprised of continuous metal.

[0089] In a preferred embodiment, Ag nanoparticles (with a ligandcoating) are combined with AgBF₄ salt, and an electron deficienttwo-photon absorbing dye in polyvinylcarbazole, to form a composite. Inan example of exposure with radiation for writing of a metal pattern,100 fs laser pulses at a wavelength of 730 nm are focused onto the filmresulting in the formation of reflective and conductive Ag metal at thepoints of exposure. Preferably, the laser wavelength ranges from 157 nmto 1.5 μm for one-photon excitation and from 300 nm to 3.0 μm fortwo-photon excitation. The pulse width of the laser is preferably in theorder of ≦1 μs to 10 fs for two-photon excitation. Arbitrary patterns ofAg metal can be written by moving the point of focus in the film.Writing of microscale lines, rectangular shapes and various 3D patternsof metal lines has been accomplished with this method. Many variationsin the step of exposure with radiation are possible, as would be knownto those skilled in the art of radiation induced change of materialsproperties. For example, electron beams, electrical current via ascanning probe tip, focused ion beams, γ-radiation, x-rays, UV-rays,VUV-rays, neutron beams, and neutral atom beams may be used in themethod of the present invention.

[0090] Formation and Growth of Metal Nanoparticles

[0091] It is known that the formation of alkylthiolate coated metalnanoparticles proceeds via a nucleation-growth mechanism (Hostetler, M.J. et al., Alkanethiolate gold cluster molecules with core diametersfrom 1.5 to 5.2 nm; Core and monolayer properties as a function of coresize. Langmuir, 14, 17-30 (1998)) that involves the formation of alayered stoichiometric compound as a first step as illustrated below forAg:

[0092] nAg⁺+nRSH→(AgSR)_(n)+H⁺

[0093] followed by a second step involving growth. The second step canbe due to the presence of silver zero atoms:

[0094] (AgSR)_(n)+mAg⁰→Ag^(n),(SR)_(n)

[0095] with n′=n+m

[0096] or to the presence of an agent that reduces the metal ions of thelayered compound themselves:

[0097] (AgSR)_(n)→Ag_(n)(SR)_(m)+m′RSSR

[0098] with 2 m′=n−m

[0099] Once generated, these nanoparticles are soluble materials thatare processable with standard methods. In particular, their solubilityin organic solvents allows for a multiplicity of processing techniquesbased on which films of nanoparticles or solid matrices withincorporated nanoparticles can be created. We teach that, with such ananoparticle film or composite, the growth of nanoparticles may bedriven such that they increase in size, and contact and fuse with othernanoparticles. When this process occurs to a sufficient extent, then acontinuous metallic feature (single or polycrystalline) will be formed.

[0100] One important contribution of the present invention is that itteaches the materials and exposure conditions that allow the growth ofpre-nucleated metal nanoparticles in solid state. By the termpre-nucleated metal nanoparticle we mean a metal nanoparticle which hasbeen nucleated and grown in a preceding synthetic process. Theseconditions allow nanoparticles to grow to the point wherein theycollapse in a continuous metallic feature.

[0101] Several growth processes are disclosed that vary in the method bywhich the metal atom (zero oxidation number) is generated from its ion.

[0102] The first case (case 1) makes use of the generation of the metalatom from the metal ion using an electron beam. The electron beam candirectly reduce the silver ion or can generate a radical anion that thenreduces the metal ion or can ionize a molecule and the electron thenreduces the metal ion.

[0103] An advantage of case 1 is the versatility in the metal lineresolution that can be achieved, which can range from several microns(with the use of a mask and a large electron beam) to few nanometers(with the use of conductive scanning probe microscopy tips, forexample). FIG. 1 is a schematic illustration of a case 1 growth process.In the upper drawing an injected electron reduces a metal ion; in thelower part it generates a radical anion that subsequently reduces themetal ion. In particular, conductive tip Atomic Force Microscopy, inwhich the tip of the microscope approaches a film in tapping mode, canbe used as source of electrons. Once it is positioned within fewnanometers away from the surface of the nanoparticles it injectselectrons into the nanoparticle film to generate metal lines whosethickness may be just a few nanometers.

[0104] The second case (case 2) is that wherein metal ions are reducedto their zero oxidation number through a local increase in temperaturewhich is caused by absorption of light energy (preferably a laser beam)by a dye molecule and the transfer of the absorbed energy to heat.Materials and methods for the non-linear local heating of materials aredescribed in U.S. Pat. No. 6,322,931 which is incorporated herein byreference.

[0105] The third case (case 3) is to photoexcite a molecule so as tocreate an excited state, thus increasing the reducing potential of themolecule by a sufficient amount that it can reduce the metal ion,whereas the ground state could not. In this process the dye is oxidizedso, in many cases, a sacrificial donor may be required in order toregenerate it. FIG. 2 illustrates an energy level scheme for sensitizedmetal ion reduction. In the first step (black) an electron is promotedfrom the highest occupied molecular orbital (HOMO) level of the dye toone of its excited states. From this level the electron either goesdirectly to the metal ion (red) or first to the lowest unoccupiedmolecular orbital (LUMO) of an electron transporting material (blue) andthen to the metal ion. Subsequently, an electron may transfer (green)from the HOMO of the sacrificial donor to the HOMO of the dye, therebyregenerating the neutral dye. The sacrificial donor and the electrontransporting material are not necessary.

[0106] The feature size resolution achievable in this case depends onthe type of photo excitation. The lower limit on the feature size can beseveral microns is diffraction limited for one photon (case 3a)irradiation, is potentially smaller for multi-photon irradiation, due tothresholding effects (case 3b), and is in the order of tens ofnanometers for near field irradiation (case 3c). In this case the limitis determined by the near-field source dimension and its positionrelative to the film.

[0107]FIG. 3 illustrates the writing of metal features in a nanoparticlecomposite. The red cone represents the laser beam and the darker spot atits end represents the focus of the beam. The gray rectangle is thecomposite film containing the dye and the salt in it, while the bluecircles represent the nanoparticles. Upon exposure, growth andcoalescence, a metal pattern is formed. In the upper part (a), the metalatoms are formed in the beam focus and they start to migrate towardnanoparticles, then (b) the nanoparticle starts to grow, and finally (c)a continuous metal feature is formed. This scheme is appropriate to case2 and 3 methods.

[0108] Preferred Embodiments

[0109] Preferred examples will be given in the following section toillustrate methods of fabrication of metal. These examples are by nomeans exhaustive and it should be clear to one skilled in the art thatnumerous other procedures can be employed based upon the basicprinciples of the invention disclosed herein. Two different classes ofcompositions can be used to generate metal features. In the first classthe metal nanoparticles act as their own matrix and in the second classthe metal nanoparticles are dopants in a host matrix.

[0110] Class I

[0111] In the first embodiment the material is composed of:

[0112] i) ligand coated metal nanoparticles coated by one or more typesof organic ligands. In some cases it is advantageous to use a mixture oforganic ligands, as described above. In addition, molecules as describedin (ii) (below) could be attached to one or more types of ligandscoating the particle.

[0113] ii) a molecule (dye) whose molecular orbital energy levels aresuitable for photoreduction of the corresponding metal salt or whoselinear or nonlinear optical absorption is able to generate thesufficient heat to cause reduction the metal salt. This component can bedissolved in the nanoparticle matrix or covalently bonded to thenanoparticle as one of the ligands, or as the only ligand;

[0114] iii) a metal salt; and

[0115] iv) a sacrificial donor, that is a molecule whose molecularorbital levels are of appropriate energy to reduce the cation of the dyedescribed in (ii) above, which is formed upon photoreduction of themetal ion or upon electron-beam exposure. In this manner, the originaldye can be regenerated and can once again act as a reducing agent ofmetal. The component may be part of the host matrix structure. In somecases this component may not be necessary.

[0116] Preferred concentrations (in weight percent, based on the totalweight of the composition) for each component of the class I system areas follows and are chosen so as to add to a total of 100%:

[0117] Component (i): 55 to 100%, including all values and subvaluestherebetween, especially including 60, 65, 70, 75, 80, 85, 90 and 95%;

[0118] Component (ii): 0 to 15%, including all values and subvaluestherebetween, especially including 2, 4, 6, 8, 10, 12 and 14% (0 appliesfor the case where the nanoparticles have dye terminated ligands intheir outside shell);

[0119] Component (iii): 0 to 15%, including all values and subvaluestherebetween, especially including 2, 4, 6, 8, 10, 12 and 14%;

[0120] Component (iv): 0 to 10%, including all values and subvaluestherebetween, especially including 2, 4, 6, and 8%.

[0121] Class II

[0122] In the second embodiment a material acts as a host matrix inwhich the other components i)-iv) are dispersed or dissolved:

[0123] v) a matrix that dissolves all the other components. This matrixcan be:

[0124] a) a polymer;

[0125] b) a glass;

[0126] c) a highly viscous liquid;

[0127] d) a liquid crystalline material or polymer, or mesoscopic phase;and

[0128] e) a porous crystalline or amorphous solid.

[0129] In the case (a) of component (v) there could be circumstances inwhich it is particularly advantageous to add an additional component(vi):

[0130] vi) a plasticizer, that is a molecule capable of lowering theglass transition temperature of the polymer, thereby rendering itsmechanical properties more suitable for the application.

[0131] In both cases the component (ii) is not necessary when the sourceof irradiation is an electron beam.

[0132] Preferred concentrations (in weight percent, based on the totalweight composition) of the for each component of the class II system areas follows and are chosen so as to add to a total of 100%:

[0133] Component (i): 0.05% to 25%, including all values and subvaluestherebetween, especially including 0.1, 0.2, 0.5, 1, 2, 3, 4, 5, 10, 15and 20%;

[0134] Component (ii): 0 to 15%, including all values and subvaluestherebetween, especially including 2, 4, 6, 8, 10, 12 and 14% (0 applieswhere the nanoparticles have dye terminated ligands in their outsideshell, or either the host or the plasticizer have a suitable dye assubunit);

[0135] Component (iii): 0 to 25%, including all values and subvaluestherebetween, especially including 5, 10, 15 and 20%;

[0136] Component (iv): 0 to 60%, preferably from 20% to 60%, includingall values and subvalues therebetween, especially including 10, 20, 30,40 and 50%;

[0137] Component (v): 0.5-99.5%, including all values and subvaluestherebetween, especially including 10, 20, 30, 40, 50, 60, 70 and 80%;and

[0138] Component (vi): 0 to 70%, including all values and subvaluestherebetween, especially including 10, 20, 30, 40, 50 and 60%.

[0139] Description of the Components

[0140] Component (i): Metal Nanoparticles

[0141] Preferred examples of component (i) are:

[0142] ii) metal (e.g. silver, gold, copper, and iridium) nanoparticleswith dimensions from 1 to 200 nm (diameter) coated with organic ligands(Kang, S. Y. & Kim, K., Comparative study of dodecanethiol-derivatizedsilver nanoparticles prepared in one-phase and two-phase systems.Langmuir, 14, 226-230 (1998); Brust, M., Fink, J., Bethell, D.,Schiffin, D. J. & Kiely, C., Synthesis and Reactions of FunctionalizedGold Nanoparticles. Journal of the Chemical Society-ChemicalCommunications, 1655-1656-(1995); Brust, M., Walker, M., Bethell, D.,Schiffrin, D. J. & Whyman, R., Synthesis of Thiol-Derivatized GoldNanoparticles in a 2-Phase Liquid-Liquid System. Journal of the ChemicalSociety-Chemical Communications, 801-802 (1994));

[0143] i2) nanoparticles composed of alloys of metals coated withorganic ligands (Link, S., Burda, C., Wang, Z. L. & El-Sayed. M. A.,Electron dynamics in gold-silver alloy, nanoparticles: The influence ofa nonequilibrium electron distribution and the size dependence of theelectron-phonon relaxation. Journal of Chemical Physics, 111, 1255-1264(1999); Link, S., Wang, Z. L. & El-Sayed, M. A., Alloy formation ofgold-silver nanoparticles and the dependence of the plasmon absorptionon their composition. Journal of Physical Chemistry B, 103, 3529-3533(1999));

[0144] i3) uncoated metal nanoparticles (for the second embodiment)(Heilmann, A. & Kreibig, U., Optical properties of embedded metalnanoparticles at low temperatures. European Physical Journal-AppliedPhysics, 10, 193-202 (2000)); and

[0145] i4) metallic nanoshells whose cores are semiconductor, metaloxide, silicate, polymer, or biopolymer nanoparticles and whose outershells are metallic, the metallic part being with or without (for thesecond embodiment) an organic coating (Wiggins, J., Carpenter, E. E. &O'Connor, C. J., Phenomenological magnetic modeling of Au:Fe:Aunano-onions. Journal of Applied Physics, 87, 5651-5653 (2000);Carpenter, E. E. et al., Synthesis and magnetic properties ofgold-iron-gold nanocomposites. Materials Science and Engineeringa-Structural Materials Properties Microstructure and Processing, 286,81-86 (2000)).

[0146] Components i1, i2, i3 are made of nanopatticles that can becoated by organic ligands. These ligands are molecules that areessentially composed of three parts in the following scheme: A-B-C.

[0147] Part A is a molecular or ionic fragment that has at least oneatom having a lone pair of electrons that can bond to a metalnanoparticle surface, or is an unsaturated molecular or ionic fragmentthat can bond to the metal nanoparticle surface, and includes a point ofattachment to connect the fragment to B. Some examples include: ^(e)S,^(e)O—, ^(e)O₂C—, ^(e)S—S—R, ^(e)O₃S—, ^(e)S₂C—NR—, ^(e)O₂C—NR—,P(R₁R₂)—, N(RR₂)—, O(R₁)—, P(OR₁)(OR₂)O—, and S₂(R)—, where R, R₁, andR₂ may be independently selected from the group consisting of —H, alinear or branched alkyl chain containing 1 to 50 carbon atoms, phenylor other aryl groups, and hetero aromatic groups.

[0148] Part B is an organic fragment that has two points of attachment,one for connecting to part A and one for connecting to part C. Thisfragment serves to provide bulk around the nanoparticle to helpstabilize it against fusing with other nanoparticles. Part B can benothing (a single bond) or can be independently selected from the groupconsisting of a methylene chain with 1 to 50 carbon atoms, a phenylenechain with 1 to 20 phenyls, a thiophlenylene chain with 1 to 20thiophenylenes, phenylene vinylene chains with 1 to 20 phenyl vinylenes,branched hydrocarbon chains with 2 points of attachment, ethylene oxidechains with 1 to 20 ethylene oxides, oligo(vinyl carbazole) chains with1 to 20 vinyl carbazole units and points of attachment at each end ofthe chain.

[0149] Part C is a molecular fragment with one point of attachment thatconnects to fragment B. This group may be used to impart specificfunctions to the exterior of the ligand coated nanoparticle such as,compatability with a matrix, photoreducing properties, two-photonabsorption properties, self-assembly properties, chemical attachmentproperties. Part C can be independently selected from the groupconsisting of —H, phenyl, naphthyl, anthryl, other aryl groups,N-carbazoyl, α-fluorenyl, —SiOR₃, —SiCl₃, any group described as apossible Part A fragment, photoreducing dyes, two-photon absorbingchromophores, a multi-photon absorbing chromophore methylene blue,oligonucleotide strand, peptide chain, or any group described as apossible part B fragment where one of the points of attachment issubstituted with a hydrogen.

[0150] The preferred nanoparticles of the present invention may have amixture of two or more types of ligands, each one with its owncharacteristic groups and functionality.

[0151] For the sake of clarity some specific examples of ligands thathave been used for class (i1) are mentioned hereafter: Ligand Ligandstructure Ligand chemical name label

Octanethiol I₁

Dodecanethiol I₂

Heptanethiol I₃

8-(9H-carbazol-9-yL)octane-1- thiol I₄

8-(9H-carbazol-9-yl)dodecane-1- thiol I₅

3-mercaptopropanoic acid I₆

Bis[2-(dimethylamino)ethyl]2- mercaptopentadioate I₇

3-{2,5-bis[(E)-2-(4-formyl-(phenyl)ethenyl]phenoxy}propyl-4-(1,2-dithiolan-3- yl)butanoateI₈

[0152] Examples of preferred metal and ligand combinations are thefollowing: Metal Ligand Given name silver I₁ nAg1 silver I₂ nAg2 silverI₃ nAg3 silver I₄ nAg4 silver I₇ nAg5 silver I₁ + I₄ nAg6 silver I₁ + I₂nAg7 silver I₁ + I₇ + I₄ nAg8 silver I₁ + I₄ + I₈ nAg9 gold I₁ nAu1 goldI₂ nAu2 copper I₁ nCu1 copper I₁ nCu2

[0153] Component (ii) Photoreducing Dyes

[0154] Preferred examples of component (ii) are:

[0155] Class 1: Centrosymmetric bis(aldehyde)-bis(styryl)benzenes

R₁ = H R₂ = H 1a R₁ = OCH₃ R₂ = H 1b R₁ = OCH₃ R₂ = OCH₃ 1c R₁ = OC₁₂H₂₅R₂ = H 1d R₁ = OC₁₂H₂₅ R₂ = OCH₃ 1e

[0156] Class 2: Non-centrosymmetric bis(aldehyde)-bis(styryl)benzenes

R₁ = H R₂ = H R₃ = H 2a R₁ = OCH₃ R₂ = H R₃ = H 2b R₁ = OCH₃ R₂ = OCH₃R₃ = H 2c R₁ = OC₁₂H₂₅ R₂ = H R₃ = H 2d R₁ = OC₁₂H₂₅ R₂ = OCH₃ R₃ = H 2e

[0157] Class 3: Centrosymmetric acceptor terminated bis(styryl)benzenes

R₁ = H R₃ = H R₂ =

1a R₁ = OCH₃ R₃ = H R₂ =

1b R₁ = OCH₃ R₃ = OCH₃ R₂ =

1c R₁ = OC₁₂H₂₅ R₃ = H R₂ =

1d

[0158] Class 4: Non-centrosymmetric acceptor terminatedbis(styryl)benzenes

R₁ = H R₂ = OCH₃ R₃ = H R₄ =

1a R₁ = OCH₃ R₂ = OC₁₂H₂₅ R₃ = H R₂ =

1b R₁ = OCH₃ R₂ = H R₃ = OCH₃ R₂ =

1c R₁ = OC₁₂H₂₅ R₂ = OCH₃ R₃ = OCH₃ R₂ =

1e

[0159] Class 5: Other dyes

[0160] The dye can be a donor-acceptor dye such as those described inU.S. Pat. No. 5,804,101; U.S. Pat. No. 6,090,332; U.S. Pat. No.5,670,090; U.S. Pat. No. 5,670,091 and U.S. Pat. No. 5,500,156 which areincluded herein by reference.

[0161] Component (iii:) Metal Salts

[0162] Preferred examples of component (iii) are any metal(I) solublesalt, including silver tetrafluoroborate (AgBF₄); silverhexafluoroantimonate (AgSbF₆); silver diethyldithiocarbamate(C₃H₁₀NS₂Ag); silver nitrate (AgNO₃);

[0163] trimethyl phosphite cuprous iodide (ICuP(OCH₃)₃); andchlorotrimethyl phosphite gold (C1AuP(OCH₃)₃).

[0164] Component iv): Matrices

[0165] The main requirement of this component is to have the ability todissolve all the other components and to form a homogeneous composite.

[0166] Preferred examples of component (v) are:

[0167] a) Polymer a₁: poly(9-vinylcarbazole)

[0168] In most of the examples given below the polymer actually used wasthe secondary standard (Aldrich chemicals) whose M_(n)=69,000;

[0169] Polymer a₂:poly(2-{[11-(9H-carbazol-9-yl)undecanoyl]oxy}ethyl-2-methylacrylate)PCUEMA

[0170] Polymer a₃: poly (4-chloro styrene); and

[0171] Polymer a₄: poly (methylmethacrylate) PMMA;

[0172] b) SiO_(x), organically modified SiO_(x) materials, TiO_(x),(SiO_(x))_(n)(TiO_(x))_(m)

[0173] c) viscous liquid host:

[0174] Other Components

[0175] Preferred examples of component (iv) and of component (vi) areethylcarbazole which is a good plasticizers for polyvinyl carbazole, anda sacrificial donor;

[0176] terminal di(9-carbazoyl) alkanes which are good plasticizer andsacrificial donors;

[0177] 0≦n≦10

[0178] and the following molecule which is a sacrificial donor:

[0179] Applications of the present invention include: writing of metalline diffraction gratings for light waves in integrated optics,patterning of microelectrode arrays for applications in electrochemistryor biology, patterning of metal wires for integrated circuitinterconnection, for example in hard wiring of security codes on chips,and in chip repair. Additional applications include: fabrication ofnanometer size metal wires, single electron transistors, and othercomponents for nanoelectronics applications; 3D interconnection ofelectronic components in multilevel integrated circuits; fabrication ofmetallic devices for microsurgical applications; antennae and arraysthereof for terahertz radiation, formation of mirrors of differentangles of inclination within a thin film metallic photonic crystal andphotonic crystal waveguides, and metallic microsensors, micro-resonatorsand microelectromechanical structures. This invention can be used forthe wiring of nanoscale and single molecule based electronic devices.

[0180] Further, the present invention offers the following advantagesover the currently available technology:

[0181] i) Continuous metal lines can be formed in three dimensionalpatterns with a resolution in the micro- or nanoscale with fewlimitations on the shape of the pattern.

[0182] ii) The process does not require the generation of hightemperatures as needed in pyrollytic processes, and thus can be utilizedin the integration of nanoscale devices or in conjunction with thermallysensitive substrates.

[0183] iii) Metal patterns or structures can be produced on a widevariety of substrates. Preferred substrates are silicon, glass orplastic substrates, all of which may be covered with, for example,indium-tin-oxide (ITO). Further preferred substrates are Au, Ag, Cu, Al,SiO_(x), ITO, a hydrogel or a biocompatible polymer.

[0184] iv) The material systems are easy to process and simple tohandle, as opposed to highly toxic gas phase organometallic precursorsas typically used in chemical vapor deposition.

[0185] v) Inert atmospheres are not required.

[0186] vi) High vacuum equipment is not needed.

[0187] vii) The fact that the process is thresholded allows the sampleto be handled under ambient lighting and thermal conditions, thus givingthe samples exceptional long-term stability, for example, a shelf lifeof 8 months in the dark.

[0188] However, the process of the present invention is not limited toambient temperatures. If Class I compositions are used, a temperaturerange of from −270 to 200° C. is preferred. If Class II compositions areused, a temperature range of from −250 to 150° C. is preferred.

[0189] Thus, the present invention relates to a novel process fordirectly writing three-dimensional metal patterns in a materialrequiring low energy as described in Examples 20 and 21, below and lowtemperature as stated above. The versatility of the compositions withregard to the type of metal nanoparticles used and the type of dyeoffers many possibilities for engineering of materials for specificapplications.

[0190] There are many possible applications that can be embodied basedon the present invention.

[0191] One set of applications involves the ability to induce largechanges in the physical properties in a matrix generated by the presenceof dispersed nanoparticles (1-100 nm), dispersed small metal island (100nm-100 μm), quasi-continuous (percolated) metal or continuous metallines. These modifications alter the optical properties, such asrefractive index of a solid state matrix, and such changes in propertiesare useful in optical data storage, in creating diffractive opticaldevices, or in defining waveguiding regions for integrated optics, orwriting of metal line diffraction gratings for light waves in integratedoptics.

[0192] This invention can be used for optical data storage in manyformats. Information can be stored in 3D using two-photon excitation towrite bits comprised of regions containing metal nanoparticles or metalislands. A focused beam is useful in this regard, but crossing beams orinterfering beams, such as in holography, can be employed.

[0193] Another example of optical data storage is where thephotosensitive metal nanoparticle composite is used as an opticalrecording layer for recordable compact disk-like applications.

[0194] A very attractive application is for ultra-high density 2Doptical data storage using near field light source to write very smallbits (˜100 nm or smaller).

[0195] Other optical applications include: fabrication of reflectivepolarizers, switchable gratings, and micromirrors.

[0196] A second set of applications of the present invention uses directpatterning of conductive metal features. They include: patterning ofmicroelectrode arrays for applications in electrochemistry or biology,patterning of metal wires for integrated circuit interconnection, forexample in hard wiring of security codes on chips, and in chip repair.Additional applications include: fabrication of nanometer size metalwires, single electron transistors, and other components fornanoelectronics applications; 3D interconnection of electroniccomponents in multilevel integrated circuits; writing of contacts onsoft materials such as organic light emitting diodes or organic fieldeffect transistors; fabrication of metallic devices for microsurgicalapplications, such as needles and stents (McAllister, D. V., Allen, M.G. & Prausnitz, M., R., Micrafabricated microneedles for gene and drugdelivery. Annual Review of Biomedical Engineering, 2, 289-313 (2000);Polla, D. L. et al., Microdevices in medicine. Annual Review ofBiomedical Engineering, 2, 551-576 (2000); Santini, J. T., Richards, A.C., Scheidt, R., Cima, M. J. & Langer, R., Microchips as controlleddrug-delivery devices. Angewandte Chemie-International Edition, 39,2397-2407 (2000); Rymuza, Z., Control tribological and mechanicalproperties of MEMS surfaces. Part 1: critical review. MicrosystemTechnologies, 5, 173-180 (1999)); and micro-electromechanical structures(Walker, J. A., The future of MEMS in telecommunications networks.Journal of Micromechanics and Microengineering, 10, R1-R7 (2000);Spearing, S. M., Materials issues in microelectromechanical systems(MEMS). Acta Materialia, 48, 179-196 (2000); Lofdahl, L. & Gad-el-Hak,M., MEMS applications in turbulence and flow control. Progress inAerospace Sciences, 35, 101-203 (1999)). The materials and methods ofthis invention can be used for the wiring of nanoscale and singlemolecule based electronic devices (Quake, S. R & Scherer, A., Frommicro- to nanofabrication with soft materials. Science, 290, 15361540(2000)).

[0197] Yet other applications can include uses of written metal featuresin hybrid electrooptical applications, where both the electrical andoptical properties are exploited. An example could be an electrode arrayshaped so to act as a diffractive grating that may be backfilled byliquid crystalline material whose alignment is controlled by the appliedfield. The liquid crystal alignment would control the optical propertiesof the grating.

[0198] Writing of conductive metal features is also of advantage toapplications in microfluidics. For example, in the fabrication ofelectroded channels to control fluid flow, to drive electrophoreticseparations, to drive electrochemical reactions, or to monitor thedielectric properties of the channel contents.

[0199] Another application of the invention is the patterning orfabricating of templates (Ostuni, E., Yan, L. & Whitesides, G. M., Theinteraction of proteins and cells with self-assembled monolayers ofalkanethiolates on gold and silver. Colloids and SurfacesB-Biointerfaces, 15, 3-30 (1999)) which can be used for deposition,self-assembly, or templated growth of other materials or compounds. Forexample, patterned metals surfaces can be used for the generation ofpatterned arrays of self-assembled molecules such as thiols, carboxylicacid or other functionalized compounds. One can drive reactions at themetal surfaces by using gas phase, solution phase or solid phasereactants. The patterned surfaces can also be exploited for thepatterned catalysis of chemical reactions.

[0200] Yet another application of the ability to write metal features ina free form fashion is to create electrode patterns which can be used todirect the growth and interconnection of neurons or other types ofcells.

[0201] Having generally described this invention, a furtherunderstanding can be obtained by reference to certain specific exampleswhich are provided herein for purposes of illustration only, and are notintended to be limiting unless otherwise specified.

EXAMPLES

[0202] Discussion of the Examples

[0203] The following discussion is meant to encompass a set of examplesof some important experiments and to assist in the understanding of theexamples section.

[0204] This discussion mainly focuses on the possibility to write 3Dmetallic patterns with multiphoton irradiation (class II, case 3). This,is a good test for all other classes and cases described above. In fact,most of the steps involved in the present invention are common to allthe different cases described and namely they are

[0205] 1. the synthesis of highly soluble nanoparticles,

[0206] 2. the preparation of a homogeneous and optical quality matrix,and

[0207] 3. the post-writing processing and characterization.

[0208] These steps are common to all different kinds of writingprocesses. The solution of the problems involved in these partsconstitutes a large part of the present invention.

[0209] To generate a homogeneous matrix with good optical quality it isnecessaries to find (i) a solvent or a solvent mixture capable ofdissolving all the components and (ii) a matrix (a polymer) that iscapable of dissolving all the components in solid state. Preferredsolvents are chloroform, dichloromethane, acetonitrile, acetone, water,hexane, heptane, pentane, toluene, dichlorobenzene, dichloroethane andmixtures thereof. A solution of chloroform/acetonitrile 20/1 in volumewas found to be the best one for this purpose and polymers a₁ and a₄have the desired properties to efficiently dissolve a wide variety ofsilver salts, while PMMA shows the ability of dissolving copper salts. Amore complex problem is the solubility of nanoparticles both is organicsolvents and in solid matrices.

[0210] It has been found that despite the wide variety of ligands thatcan be attached on nanoparticles their solubility remains limited. Inorder to overcome this problem it is important to use nanoparticles witha mixture of ligands. Examples of suitable ligands have been providedabove. The use of a mixture of ligands adds entropy to the system andmainly limits the interdigitation between ligands that is the main causefor poor solubility (Voicu, R., Badia, A., Morin, F., Lennox, R. B. &Ellis, T. H., Thermal behavior of a self-assembled silvern-dodecanethiolate layered material monitored by DSC, FTIR, and C-13 NMRspectroscopy. Chemistry of Materials, 12, 2646-2652 (2000); Sandhyarani,N., Pradeep, T., Chakrabarti, J., Yousuf, M. & Sahu, H. K., Distinctliquid phase in metal-cluster superlattice solids. Physical Review B,62, 8739-8742 (2000); Sandhyarani, N. & Pradeep, T., Crystalline solidsof alloy clusters. Chemistry of Materials, 12, 1755-1761 (2000); Badia,A. et al., Self-assembled monolayers on gold nanoparticles. Chemistry-aEuropean Journal, 2, 359-363 (1996)). In addition, particular groupswere used to make the particle more soluble in their host, e.g.carbazole terminated alkanethiol as one of the ligands to make theparticle soluble in polyvinylcarbazole.

[0211] The best strategy to synthesize these nanoparticles was the useof a monophase reaction in ethanol (Example 1), the simple addition ofdifferent ligands in different ratios was effective in obtainingparticles with different ligands on their outer shell and with adrastically reduced enthalpy of melting (Example 2).

[0212] If the particles are soluble enough, the casting of the filmsbecomes relatively easy and can be done either via solvent evaporation(Example 8) or by spin coating (Example 17). In the first case theachievable range of thickness spans from few microns (Example 13) to 200μm. The maximum silver salt loading ratio achievable in polymer a₁ is15% (by weight) for silver tetrafluoroborate; in the same polymer 5% isthe maximum for dye 1d, and 3% is the maximum for nAg6 (Example 9). Theloading ratio maxima are slightly higher in the case of spin coatingtechniques.

[0213] The solid state growth of metal nanoparticle has been exploredand proven through a series of experiments involving the photochemicalreduction of silver ions in a matrix. The carbazole moiety plays therole of sacrificial anode too, thus allowing the possibility of dopingthe silver with a smaller amount of photoreducing dye.

[0214] Polyvinylcarbazole has a T_(g) of around 200° C. so a plasticizerwas used in order to lower the glass transition temperature to close toroom temperature. A well known plasticizer for this polymer has beenused: ethylcarbazole. The range of compositions of the film that wasmostly used was (all percentages in weight) 30-50% of plasticizer, 3-5%dye 1d, 10-15% AgBF₄, 0.2-3% nAg6. The amount of plasticizer includesall values and subvalues therebetween, especially including 33, 36, 39,42, 45. and 48% by weight. The amount of dye includes all values andsubvalues therebetween, especially including 3.2; 3.4; 3.6; 3.8; 4.0;4.2; 4.4; 4.6 and 4.8% by weight. The amount of AgBF₄ includes allvalues and subvalues therebetween, especially including 10.5; 11; 11.5;12, 12.5; 13; 13.5; 14 and 14.5% by weight. The amount of nAg6 includesall values and subvalues therebetween, especially including 0.4; 0.6;0.8; 1.0; 1.2; 1.4; 1.6; 1.8; 2.0; 2.2; 2.4; 2.6 and 2.8% by weight.

[0215] Reference films with the same composition but withoutnanoparticle were also made. All the films made in this way had goodoptical quality and were perfectly homogeneous by naked eye inspection,though some defect could be observed, none was perfect under themicroscope (60× magnification).

[0216] All films were irradiated with a tightly focused infrared lightsource (from 700 to 800 nm 100 fs pulse-length) generated silver lines(Example 22) and or islands (squares in particular) while thecorresponding reference film did not generate any visible feature.Further inspections of the reference film either using opticalspectroscopy or TEM microscopy lead to the conclusion that smallnanoparticles which have a large size dispersion are generated. Thefeatures generated in polymer films that contained metal nanoparticlescould be separated from their matrix via dissolution of the matrix in anappropriate solvent mixture and then studied with XPS (Example 10) andSEM techniques (Example 9).

[0217] XPS Results show that the generated features are made mainly ofsilver in its zerovalent (metallic). The latter technique shows thatthree-dimensional features can be formed and that the generated linesare continuous up to a micron level.

[0218] A more complex experiment was done in order to study our processwith a TEM microscope: three identical films were castes of copper grids(Example 11) and two of them were exposed to irradiation with ananosecond laser (532 nm), the first one was irradiated by a singlelaser shot (125 mJ) and the second one by three shots.

[0219] The result was that the average radius of the particle doubledafter one laser shot but their number per unit area stayed the same, allin agreement with the proposed mechanism (FIG. 9).

[0220] Many variations are possible, including the use of near fieldexcitation. In order to check the feasibility of this variation thethreshold power required for the writing was check and it was discoveredto be approx. 10⁸ W/m² for single photon excitation (Example 20) and 10⁹W/m² for two photon excitation (Example 21). The power thresholds areconsistent with those available for near field writing. The experimentalsection contains many different kinds of films that have been preparedusing different kind of polymers (Example 15) or matrices, dyes (Example14), salts or nanoparticles (Example 12).

[0221] Important issues in the developing step have been solved. Inorder to provide a chemical bond between the structures and thesubstrate a two step method for functionalizing the substrate wasdeveloped. In the first step a monolayer of thiol terminated moleculesis created in the glass substrate. This monolayer is bound to thesubstrate via trimethoxy silane functionalities. In the second step ananoparticle monolayer is introduced on the first monolayer and theparticles are chemically bound to the thiols. This kind offunctionalized substrate drastically improved the adhesion and successin the developing step. FIG. 8 is a schematic drawing of the attachmentof a ligand capped metal nanoparticle to a thiol functionalized glasssubstrate.

[0222] In order to test for the importance of the presence of silvernanoparticles in the precursor, we irradiated film F13 (Example 25) formore than one hour in a UV chamber to see if any characteristicnanoparticle absorption band would arise in the optical absorptionspectrum or if any metal feature could appear. Only a bleaching of thedye band was observed and absolutely no evidence of continuos silvermetal or nanoparticle formation, (as evidenced by optical absorption)was observed, even under such extreme irradiation conditions.

[0223] Functionalized Metal Nanoparticles for the fabrication ofcontinuous metal features

[0224] Silver nanoparticles were synthesized with coatings of differentorganic ligands. Some of the ligands possessed groups capable ofreducing, from their excited state, silver ions to the neutral atom. Thestructures of these ligands are shown in the schematic drawing below.Three dye-ligands are used to synthesize electron and photo-activenanoparticles. The names and the ligand shell composition of theparticles used in some experiments are listed in the legend below.

R = NO₂ I₉ N(CH₂CH₃)₂ I₁₀ NC═O I₁₁ Metal ligands Given Name Silver 1₁ +1₂ + 1₉ nAg10 Silver 1₁ + 1₂ + 1₁₀ nAg11 Silver 1₁ + 1₂ + 1₁₁ nAg12Silver 1₉ nAg13

[0225] The synthesis of the ligand coated particles was a place exchangereaction (Hostetler, M. J., Templeton, A. C. & Murray, R. W. Dynamics ofplace-exchange reactions on mono layer-protected gold cluster molecules.Langmuir 15, 3782-3789 (1999)). Starting from a solution of nAg7 and thedesired ligand we were able to synthesize particles with dye moleculesin their outside shell. A different synthesis was used to obtainnanoparticles completely coated by dye attached ligands (Example 29). Inthis case silver ions were reduced with NaBH₄ in the presence of ligandI₉.

[0226] Mixtures of these particles and a silver salt gave rise to largerparticles (up to the continuous limit) upon excitation (light orelectron beams) both in solution and the solid state. A few examples,that are not representative of the full potentiality of these particles,will be discussed hereafter. The main advantage of these materialssystems that is that films of these particles are precursors for bothe-beam and light-induced growth of continuous metal features.

[0227] In order to test the reactivity of composite materials containingdye-coated particles, a series of experiments were performed on a set offour films:

[0228] Films containing nanoparticles with reducing dyes on their ligandshell (nAg11) and 2% wt. of silver salt (AgBF₄). (F14, F18)

[0229] Films of nanoparticles with reducing dyes on their ligand shell(nAg11) and no silver salt. (F15) F19)

[0230] Films of nanoparticles with no reducing dyes on their ligandshell (nAg7) and 2% wt. of silver salt (AgBF₄). (F16, F20)

[0231] Films of nanoparticles with no reducing dyes on their ligandshell (nAg7) and no silver salt. (F17, F21)

[0232] The reactivity of films with a thickness of ˜20 nm was tested ina scanning electron microscope (SEM). Film (i) was shown to be anefficient precursor for continuous metal features. In fact, combinationsof squares and lines could be written using the electron beam of themicroscope. The unreacted film could be washed away following patterningwith dichloromethane to reveal the remaining metal pattern. Thestructures before and after the washing are shown in FIG. 16. The leftimage of FIG. 16 shows an example of a square and a line written andimaged using an SEM on F14. The right image shows an example of a partof a square and a line imaged with an SEM after removal of the unexposedfilm. All the other films showed were inactive with respect to theelectron beam patterning.

[0233] The same films, cast on a glass substrate, were excited withlaser beams in order to test their photochemical activity for metalpatterning. On film (i) a series of lines was written using both visible(488 nm, 50 mW, one photon excitation) and infrared (730 nm, 250 mW,two-photon excitation) light. The written pattern was imaged before andafter removal of the unreacted nanoparticles by washing. Again Film (i)was shown to be photochemically active in forming metal patterns. Film(ii) was shown to be active as well as, but at higher incident laserpower (80 and 400 mW for one- and two-photon excitation, respectively).All the lines were written at a speed of 2 μm/s. Films iii and iv werenot photochemically active in patterning metal.

[0234] Similar experiments were conducted on films using a the electronbeam of a transmission electron microscope (TEM), with films cast onsupporting Si₃N₄ grids. The solution for film casting was the same asthat used for the SEM tests, but were diluted 10 fold in order preparesub-monolayer films. In some areas of these films, dense regions ofparticles could be found and in others well separated nanoparticle wereobserved. In all four films isolated nanoparticles with no neighboringparticles showed no significant morphological change during electronbeam exposure. Films (iii) and (iv) showed no morphological change evenin the regions that were more dense in particles. Films (i) and (ii), intheir more dense regions, showed growth of the silver particles andtheir coalescence to form semi-continuous regions. Film (i) was shown toreact quickly under electron irradiation. The reaction was slower in thefilm (ii).

[0235] The photochemical reactivity was tested on the same set of filmscast onto four separate grids. All the films were initially imagedquickly in the TEM, in order to obtain initial reference images, andthen they were irradiated with 488 nm light for 240 min. with anintensity of 1.5 W/cm². The films were then imaged again in the TEM.Only film (i) showed morphological changes. FIG. 17 illustrates theaverage changes for film (i) after electron-beam and light-inducedgrowth. FIG. 17 illustrates the laser and electron-beam induced growthof silver nanoparticles in a nanoparticle/salt composite. a, TEM imageof a composite prior to laser exposure, showing a domain of orderednanoparticles with a mean radius of 6 nm. b, Image of compositefollowing one-photon excitation at 488 nm for 240 min. with an intensityof 1.5 W/cm² (to ensure depletion of the silver salt), showing growth ofparticles. c, Image of composite prior to electron-beam irradiation,showing a domain of ordered nanoparticles with the same mean radius asin a. d, Image of composite following electron-beam irradiation in theTEM instrument for 15 min, showing growth of particles and formation ofa nearly consolidated metal domain. Scale bars: 50 nm.

[0236] The same set of tests were repeated with films based on nAg10,nAg12 and nAg13 metal particles, and the results were identical to thosedescribed above.

[0237] A thick polyvinylcarbazole (PVK) film (F22) containing nAg12 anda silver salt was cast in order to test whether such a compositematerial based on the functionalized nanoparticles would function as aprecursor for the growth of continuous metal features. The film wasmounted on a microfabrication stage and irradiated with 730 nm light (80mW). It was found that a line of silver could be written and this linewas imaged with optical microscopy (FIG. 18). FIG. 18 shows thetransmission optical microscopy of a line written in a PVK film (F22)doped with AgBF₄ and nAg12. Scale bar 30 μm.

[0238] Growth of reflective and conductive metal islands and wires in apolymeric matrix

[0239] Films with compositions described in Examples 39 and 40 were caston glass slides for two-photon microfabrication. Squares patterns ofsilver were written using rastered laser scanning. The reflectivity ofthese squares was probed with a He-Ne laser (632.8 nm). The incidentpower was 2 mW and the incidence angle was ˜30°. The written squares ofsilver showed a reflectance of 25% whereas the unexposed polymericcomposite showed a reflectance of 3%. A reflection image of the squaretaken using a confocal microscope (514.5 nm) and an interference filterfor 514.5 nm which was placed between the scan head and the microscopeand which blocks any fluorescence and allows the passage of thereflected light to the detector, is shown in FIG. 19 which illustratesthe reflection image of a silver square (right) embedded in a polymernanocomposite.

[0240] The conductance of silver lines written on a glass substrate withan array of conductive pads the surface was measured. A series ofparallel silver pads were deposited on a glass substrate using standardlithographic techniques. Half the slide was masked to allow subsequentcontacting to the pads. A series of 5 parallel lines, 200 μm long with asection of 1 μm², were fabricated at the substrate surface andperpendicular to the pads to make electrical contact between the writtenlines and the pads. The resistance of lines were measured between padsseparated by varying distances. Measurements were also made betweencontrol pads that were not connected by written lines. The bias voltagewas ramped from −2 V to +2 V, the measured current between the pads notconnected by microfabricated lines was in the range of the noise levelof the instrument (0.1 pA) indicating a huge resistance. The averageresistance measured between two neighboring pads connected by themicrofabricated lines (32 μm spacing) was 370 Ω. The resistivity (p)microfabricated lines was determined to be about 10⁻³ Ωcm, withoutcorrection for contact resistance (FIG. 20). FIG. 20 is a schematicdrawing of the slide/polymer/microfabricated line configuration used tomeasure the conductivity of the grown wires.

[0241] Microfabrication of Copper and Gold microstructures viatwo-photon excitation.

[0242] Films loaded with copper nanoparticles, copper salts and a dye1d, as described in Example 41, were cast and a pattern of copper wireswas microfabricated using two photon excitation. The same pattern wasmicrofabricated in a gold nanoparticle composite, described in example41. A 3D “stack of logs” structure was successfully microfabricated inboth composites and demonstrates that the methods described herein aregeneral and can be applied to a variety of metals. Both of thestructures are shown in FIG. 21 which is a plot of the measured I(V)curve, showing a resistance of 373 Ω.

[0243] Holographic data storage via photoinduced growth of silvernanoparticles.

[0244] The use of metal nanoparticle containing composite materials forholographic data storage was demonstrated using films described inExample 43. Two laser beams crossing at 90° (see FIG. 22 for the opticalset up) were used for holographic exposure. One of the beams (the image)was expanded and passed through a resolution test mask and the otherbeam served a plane wave reference. The holographic exposure wasperformed with an Ar⁺ ion laser (514.5 nm) with a total power of 200 mW.After exposure, the image was reconstructed with a diffractionefficiency of 8% and the reconstructed image was captured using adigital camera (see FIG. 23).

[0245]FIG. 22 shows metallic structures fabricated in nanocomposites bytwo-photon scanning laser exposure a, TOM image of copper microstructurein a different polymer nanocomposite fabricated by two-photon laserexposure. b, TOM image of a gold microstructure fabricated by two-photonlaser exposure. Scale bars: 25 μm, scale bars.

[0246]FIG. 23 shows on the left an optical set up for the writing ofholograms. On the right an optical set up for the readings of hologramsis shown. The blue ellipsoids represent focusing lenses, while the grayrectangles are mirrors. The faint gray rectangle is a 50/50beam-splitter. The black rectangle on the right is a beam stop.

[0247] Syntheses

[0248] All reagents were purchased from Aldrich and used as received.All solvents used are reagent grade unless specified.

[0249] Silver Nanoparticles

[0250] Silver Nanoparticles Capped With a single Type of Ligand (nAg1-4)

[0251] All the syntheses were done using the following procedure:

[0252] 340 mg of AgNO₃ (2 mmol) were dissolved in 100 ml of absoluteethanol at 0° C. under vigorous stirring. An amount that varied from{fraction (2/9)} to ⅔ of a millimole of the chosen ligand was dissolvedin a small amount of ethanol and added. A saturated ethanol (200 ml)solution of NaBH₄ was prepared and, 30 min after the addition of theligand, was added very slowly (over 2 hours). The solution immediatelyturned yellow and then slowly became very dark. The solution was leftstirring for additional 2 hours and then it was put in a refrigerator toflocculate.

[0253] On the next day the solution was vacuum filtered using aquantitative paper filter (VWR) with pore diameter of 1 μm and thefiltered powder was washed twice with ethanol and various times withacetone.

[0254] The yields varied from 49 to 81%.

Example 1

[0255] Synthesis of Dodecanethiol-Coated Silver Nanoparticle (nAg₁)

[0256] 330 mg of AgNO₃ (˜2 mmol) were dissolved in 200 ml of absoluteethanol at 0° C. under vigorous stirring. 58 mg of dodecanethiol({fraction (2/6)} mmol) were dissolved in 10 ml of ethanol and added tothe starting solution. A saturated ethanol (200 ml) solution of NaBH₄was prepared and, 30 min after the addition of the ligand, was addedvery slowly (2 hours). The solution immediately turned yellow and thenslowly became very dark. The solution was left stirring for other 2hours and then it was put in a refrigerator to flocculate.

[0257] On the next day the solution was filtered under vacuum using aquantitative paper filter (VWR) with a pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various times withacetone.

[0258] 190.65 mg of a black powder were collected, giving a yield of71%.

[0259] Silver Nanoparticle coated With Two or More Types of Ligands

[0260] The syntheses were done using one of two different strategies.The first strategy a) involved a one step reaction in whichnanoparticles are synthesized in the presence of multiple ligands, thesecond strategy b) involved a two step reaction in which nanoparticleundergo a ligand exchange reaction to introduce a second type of ligand.

[0261] a) For the first strategy the following approach was used:

[0262] 340 mg of AgNO₃ (2 mmol) were dissolved in 100 ml of absoluteethanol at 0° C. under vigorous stirring. A 10 ml solution of thedesired mixture of ligands was prepared. The molar ratio of the ligands$( \frac{\eta_{ligandA}}{\eta_{ligandB}} )$

[0263] was between 1 and 0.25 and the total amount was chosen so thatthe ratio between the moles of ligands and the moles of silver wasbetween {fraction (2/9)} to ⅔. 30 min after the addition of the ligand,a saturated ethanol (200 ml) solution of NaBH₄ was prepared and, wasadded very slowly (over 2 hours). The solution immediately turned yellowand then slowly became very dark. The solution was left stirring forother 2 hours and then it was put in a refrigerator to flocculate.

[0264] On the next day the solution was filtered under vacuum using aquantitative paper filter (VWR) with pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various time withacetone.

[0265] Some types of nanoparticles did not flocculate upon cooling andin those cases the solvent was evaporated under vacuum and then theresidue was suspended in water under sonication for 15 min. The waterwas then left in the hood for 2h to flocculate and then filteredaccording to the standard procedure.

[0266] The yields varied from 30 to 75%.

Example 2

[0267] Synthesis of Octanethiol-Thiol Coated silver Nanoparticle (nAg₅).

[0268] 340 mg of AgNO₃ (2 mmol) were dissolved in 200 ml of absoluteethanol at 0° C. under vigorous stirring. 24 mg of octanethiol (⅙ mmol)were dissolved in 10 ml of ethanol together with 156 mg of 14 (½ mmol)and added to the starting solution. A saturated ethanol (200 ml)solution of NaBH₄ was prepared and, 30 min after the addition of theligands, was added very slowly (2 hours). The solution immediatelyturned yellow and then slowly became very dark. The solution was leftstirring for other 2 hours and then it was put in a refrigerator toflocculate.

[0269] On the next day the solution was filtered under vacuum using aquantitative paper filter (VWR) with pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various time withacetone.

[0270] Yield: 273 mg of a black-greenish powder.

[0271] b) the second strategy was an exchange reaction

[0272] This kind of reaction was done following a known method(Hostetler, M. J., Templeton, A. C. & Murray, R. W. Dynamics ofplace-exchange reactions on mono layer-protected gold cluster molecules.Langmuir 15, 3782-3789 (1999)).

Example 3

[0273] Synthesis of Octanethiol-is Coated Silver Nanoparticle (nAg9).

[0274] Ligand exchange reaction on silver nanoparticles nAg1: The silvernanoparticles nAg1 (85.4 mg) coated with octanethiol were dissolved bystirring overnight in CH₂Cl₂. Then the ligand I₈ (14.2 mg, 0.024 mmol)is added and the dark brown solution is stirred for 5 days in theabsence of light. The CH₂Cl₂ was removed in vacuum and the brown residueis dispensed in EtOH. The particles set down overnight and can befiltered off with quantitative filterpaper and washed several times withacetone.

[0275] Yield: 17 mg. Elemental analysis: nAg9: C: 26.30, H: 4.31, S:7.38, Ag: 53.99

[0276] nAg1: C: 22.85, H: 4.62, S: 7.23, Ag: 62.50

[0277] Octanethiol: C: 66.19, H: 11.79, S: 22.07

[0278] I₈: C: 70.66, H: 6.48, S: 9.81.

[0279] Calculation based on the elemental analysis give a weight ratiofor the ligands of ca. 85 Octanethiol and 15% TMF-148. The calculatedmolar ratios are:

[0280] n₁₈/n_(Octanethiol)=0.043

[0281] n_(Ag)/n_(Octanethiol)+n₁₈=1.78 in nAg9

[0282] n_(Ag)/n_(Octanethiol)=2.25 in nAg1

[0283]¹H NMR (CDCl₃): The ¹H NMR reveals the spectrum of the ligand I₈.

[0284] Preparation of Gold Nanoparticles

[0285] Gold nanoparticles were prepared according to the procedure ofBrust (Brust, M., Walker, M., Bethell, D., Schiffrin, D. J. & Whyman, R.Synthesis of Thiol-Derivatized Gold Nanoparticles in a 2-PhaseLiquid-Liquid System. Journal of the Chemical Society-ChemicalCommunications, 801-802 (1994)).

Example 4

[0286] Synthesis Dodecanethiol-Coated Gold Nanoparticle (nAu1).

[0287] 352.8 mg of HAuCl₄*3H₂O (0.9 mmol) were dissolved in 30 ml ofdeionized water, 2.188 g of tetraoctylammoniumbromide (4 mmol) weredissolved in 80 ml of toluene. The two phases were nixed and stirred for1 h. 170 mg of dodecanethiol (0.84 mmol) were dissolved in 10 ml oftoluene and added. After 10 min 380 mg of NaBH₄ were dissolved in 25 mlof water and added all at once. Soon the organic layer became black.After 2 h the organic layer was separated and washed 3 times. Thetoluene was reduced to 10 ml under vacuum and immediately diluted to 500ml with ethanol and the solution put in a refrigerator overnight. On thenext day the solution was filtered on a qualitative filter paper andwashed with toluene multiple times.

[0288] 10 mg of a black powder were collected.

[0289] Copper Nanoparticles

[0290] Copper Nanoparticle Capped With a Single Type of Ligand

[0291] 231 mg of CuBF₄*H₂O (1 mmol) were dissolved in 100 ml of absoluteethanol (degassed by argon bubbling for at least an hour) at 0° C. undervigorous stirring in Argon atmosphere. An amount that varied from{fraction (2/9)} to ⅔ of a millimole of the chosen ligand was dissolvedin a small amount of ethanol and added. Solution immediately turnedbright yellow. After 2h a saturated (100 ml) NaBH₄ solution of degassedethanol was prepared and was added very slowly (over 3 hours). Thesolution immediately turned dark yellow and then slowly became verydark. The solution was left stirring for other 2 hours and then it wasput in a refrigerator to flocculate.

[0292] On the following day the solution was filtered under vacuum usinga quantitative paper filter (VWR) with pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various times withacetone. The whole reaction was made in controlled atmosphere.

Example 5

[0293] Synthesis of Dodecanethiol-coated Copper Nanoparticle (nCu1).

[0294] 228 mg of CuBF₄*H₂O (0.96 mmol) were dissolved in 100 ml ofabsolute ethanol (degassed by argon bubbling for at least 2 h) at 0° C.under vigorous stirring in Argon atmosphere. 51 mg of octanethiol (˜⅓mmol) were dissolved in a small amount of ethanol and added. Solutionimmediately turned bright yellow. After 2 h a saturated (100 Ml) NaBH₄solution of degassed ethanol was prepared and was added very slowly (3hours). The solution immediately turned yellow and then slowly becamevery dark. The solution was left stirring for other 2 hours and then itwas put in a refrigerator to flocculate.

[0295] On the following day the solution was filtered under vacuum usinga quantitative paper filter (VWR) with pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various times withacetone. The whole reaction was made in controlled atmosphere.

[0296] The yield was 40 mg of a black powder.

[0297] Copper Nanoparticle Coated With Two or More Types of Ligands.

[0298] 237 mg of CuBF₄*H₂O (1 mmol) were dissolved in 100 ml of absoluteethanol (degassed by argon bubbling for at least an hour) at 0° C. undervigorous stirring in Argon atmosphere. A 10 ml solution of the desiredmixture of ligands was prepared and added.

[0299] The molar ratio of the ligands$( \frac{\eta_{ligandA}}{\eta_{ligandB}} )$

[0300] was between 1 and 0.25 and the total amount was chosen so thatthe ratio between the moles of ligand and the moles of silver wasbetween {fraction (2/9)} to ⅔. After 2 h a saturated (100 ml) NaBH₄solution of degassed ethanol was prepared and was added very slowly(over 3 hours). The solution immediately turned yellow and then slowlybecame very dark. The solution was left to for other 2 hours and then itwas put in a refrigerator to flocculate.

[0301] On the following day the solution was filtered under vacuum usinga quantitative paper filter (VWR) with pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various time withacetone. The whole reaction was made in controlled atmosphere.

Example 6

[0302] Synthesis of Octanethiol-Carbazolethiol Coated CopperNanoparticle (nCu3).

[0303] 240 mg of CuBF₄*H₂O (0.974 mmol) were dissolved in 100 ml ofabsolute ethanol (degassed by argon bubbling for at least 2 h) at 0° C.under vigorous stirring in Argon atmosphere. 76 mg of octanethiol (18 ½mmol) and 35 mg of dodecanethiol (116 mmol) were dissolved in a smallamount of ethanol and added. Solution immediately turned bright yellow.After 2h a saturated (100 ml) NaBH₄ solution of degassed ethanol wasprepared and was added very slowly (3 hours). The solution immediatelyturned yellow and then slowly became very dark. The solution was left tofor other 2 hours and then it was put in a refrigerator to flocculate.

[0304] On the following day the solution was filtered under vacuum usinga quantitative paper filter (VWR) with pore diameter of 1 μm and thefilter powder was washed twice with ethanol and various time withacetone. The whole reaction was made in controlled atmosphere.

[0305] The yield was 45 mg of a black powder.

[0306] Dye and Ligand Syntheses

[0307] Most of the molecules and polymers used in the Examples wereprepared according to literature methods, the synthesis of the newmolecules is described here:

[0308] I₉

[0309]4-{2-[4-[2-(4-formylphenyl)vinyl]-2-(3-hydroxypropoxy)phenyl]vinyl}benzaldehyde(TMF-I-39): A solution of mono(diethyl)acetal terephthalaldehyde (1.75ml, 8.8 mmol) and diethyl2-(3-{[tert-butyl(dimethyl)silyl]oxy}-propoxy)4-[(diethoxyphosphoryl)methyl]benzylphosphonate (2.49 g, 4.4 mmol) in tetra hydrofuran (THF) (100 ml) wascooled to 0° C. with an ice bath. K₂CO₃ (10 ml 1 M solution in THF, 10mmol)) was added slowly via a syringe and reaction is allowed to warm upto room temperature. After stirring overnight water was added followedby 1 M HCl (50 ml) and the reaction mixture was stirred for anotherhour. The product was extracted with CH₂Cl₂ and chromatographed onsilica. The first fraction eluted with CH₂Cl₂ was rejected and theproduct was then collected using ethylacetate as solvent.Crystallization from CH₂Cl₂ gave the pure product as yellow solid (663g).

[0310]¹H NMR (CDCl₃): 10.01 (1H, s), 10.00 (1H, s), 7.88 (4H, t, J=7.5Hz), 7.67 (4H, t, J=7.5 Hz), 7.60-7.64 (3H, m), 7.12-7.24 (4H, m), 4.30(2H, t, J=6.0 Hz), 3.97 (2H, t, J=6.0 Hz), 2.20 (2H, it, J=6.0, 6.0 Hz),1.61 (1H, br s) ppm; element. anal.: calcd. C: 78.62 H: 5.86, found C:78.36H: 5.67.

[0311]3-{2,5-bis[(E)-2(4-formylphenyl)phenyl)etheny]phenoxy}-propyl5-(1,2-dithiolan-3-yl)pentanoate:

[0312] A solution of4-{2-[4-[2-(4-formylphenyl)vinyl]-2-(3-hydroxypropoxy)phenyl]vinyl}-benzaldehyde(above) (200 mg, 0.49 mmol), lipoic acid (100 mg, 0.49 mmol) andp-toluenesulfonic acid (20 mg, 0.101 mmol) was refluxed overnight in theminimum amount of CH₂Cl₂ (≈20 ml) necessary to dissolve the chromophore.The reaction mixture was poured onto a column (Al₂O₃/CH₂Cl₂) and flashchromatographed with CH₂Cl₂:Ethylacetate/10:1. The starting material wasrecovered using ethyl alcohol (EtOH).

[0313] Yield: 90 mg (31%) yellow solid.

[0314]¹H NMR (CDCl₃): 9.974 (1H, s, CHO), 9.969 (1H, s, CHO), 7.86 (2H,d, J=8.5 Hz), 7.85 (2H, d, 3=8.5 Hz), 7.65 (4H, d, J=8.0 Hz), 7.57-7.62(2H, m), 7.04-7.24 (5H, m), 4.36 (2H, t, J=6.5 Hz), 4.19 (2H, t, J=6.0Hz), 3.49 (1H, m), 3.12 (1H, m), 3.05 ( b 1H, m), 2.39 (1H, m), 2.31(2H, t, J=7.0 Hz), 2.25 (2H, m), 1.84 (1H, m), 1.57-1.69 (4H, m),1.35-1.48 (2H, m) ppm. ¹³C NMR (CDC₃l): 191.86 (CHO), 191.77 (CHO),173.65, 156.78, 144.08, 143.28, 138.09, 135.60, 135.38, 131.86, 130.47,128.27, 128.00, 127.36, 127.16, 126.52, 126.30, 120.16, 110.30, 65.19,61.33, 56.52, 40.42, 38.66, 34.76, 34.21, 29.89, 28.94, 24.85 ppm.

[0315] Polymer Synthesis (a2)

[0316] Synthesis of Carbazole Monomer c_(m):

[0317] To a solution of carbazole acid (5.0 g, 14.23 mmol) and 2hydroxyethylmethacrylate (2.0 g, 15.37 mmol) and4-dimethylamino-pyridine (0.2 g) in THF (30 ml) was added DCC (3.7 g,17.96 mmol) at room temperature. The reaction was carried out at thistemperature for 10 h. Solid was removed by filtration. After removal ofTHF, the crude product was purified by silica gel column usinghexane/ethyl acetate (9:1) as eluent. The pure product as colorless oilwas obtained in 4.2 g (63.6%).

[0318]¹H-NMR (CDCl₃, TMS, 500 MHZ): δ=8.12 (d, 2 H_(arom), J=7.5 Hz),7.479 m, 2H_(arom)), 7.42 (d, 2 H_(arom), J=7.5 Hz), 7.24 (m, 2H_(arom)), 6.13 (s, 1H, C═C—H), 5.60 (s, 1H, C═C—H), 4.35 (m, 4H, 2×OCH₂), 4.30 (t, 2H, NCH₂, J=7.5 Hz), 2.33 (t, 2H, COCH₂, J=7.0 Hz), 1.95(s, 3H, CH₃), 1.88 (m, 2H, CH₂), 1.61 (m, 2H, CH₂), 1.24 (m, 12H, 6×CH₂) ppm.

[0319]¹³C-NMR(CDCl₃, 126 MHZ): δ=173.58, 167.07, 140.34, 135.87, 126.02,125.51, 122.73, 120.29, 118.63, 108.59, 62.42, 61.82, 43.01, 34.09,29.38, 29.35, 29.30, 29.14, 29.00, 28.92, 27.26, 24.84, 18.25 ppm.

[0320] Elemental Analysis for C₂₉H₃₇NO₄ (463.61): Cald: C, 75.13; H,8.04; N, 3.02. Found: C, 75.08; H, 7.83; N, 3.28.

[0321] Synthesis of Carbazole Polymer PCUEMA:

[0322] Carbazole monomer (2.7 g, 5.82 mmol) and AIBN (14.3 mg, 0.087mmol) were dissolved in dry benzene (5.0 ml) under nitrogen. Thereaction mixture was cooled with liquid nitrogen. After onefreeze-thaw-pump cycle the reaction was heated at 60° C. for 60 h. Thepolymer was precipitated in methanol and collected by filtration. Thepolymer was dissolved in THF solution and precipitated in methanol. Thedissolution/precipitation/filtration sequence was repeated twice. Afterdrying, the white polymer was obtained in 2.65 g (98.1%) yield.

[0323]¹H-NMR (CDCL₃, TMS. 500 MHZ): δ=7.97 (d, 2 H_(arom), =8.0 Hz),7.31 (m, 2H_(arom)), 7.24 (d, 2 H_(arom), J=8.0 Hz), 7.09 (m, 2H_(arom)), 4.07 (m, 4H, 2× OCH₂), 4.01 (s, br, 2H, NCH₂), 2.17 (s, br,2H, COCH₂), 1.68 (m, 2H, CH₂), 1.45 (s, br, 2H, CH₂), 1.07 (m, 12H, 6×CH₂), 0.93 (s, br, 2H, CH₂), 0.80 (s, br, 3H, CH₃) ppm. ¹³C-NMR (CDCl₃,126 MHZ): δ=173.25, 140.30, 128.30, 125.48, 122.70, 120.26, 118.63,108.56, 62.65, 61.16, 44.82, 42.89, 33.78, 29.44, 29.35, 29.28, 29.08,28.90, 27.22, 24.74 ppm.

[0324] I₄ and I₅

Example 7

[0325] Synthesis of Ligand I₄

[0326]3.57 g. 9-carbazole-yl-octane-1-thiol (˜10 mmol) were dissolved in20 ml of dimethylsulfoxide (DMSO), 1.52 mg of thiourea (˜20 mmol) wereadded, the solution was vigorously stirred. After 2 days a concentratedaqueous solution of NaOH was added dropwise. Soon a red precipitatedformed, during the addition the precipitated redissolved again andsolution turned red. Addition was stopped upon reaching of pH 11(checked using pH paper). The solution was then neutralized addingdropwise HCl (aq. cone) and it slowly turned yellow. The organic wasthen extracted with diethyl ether (Et₂O) and washed with water threetimes. The organic solvent was dried under vacuum, and the residue wascollected.

[0327] Sample Preparation

[0328] In this section several examples of nanocomposite sampleprocessing and preparation are given. All films hereafter reported havebeen tested and metallic silver lines have been successfully writtenusing radiation in all cases on.

[0329] Samples were prepared by solvent casting or by spin coating, Mostof the samples were cast in air atmosphere, in some cases the processingwas done under argon atmosphere.

[0330] All glass microscope slides were cleaned with the followingprocedure:

[0331] a) Sonication for 1 h in water and soap and extensive rinse withDI water

[0332] b) Sonication for 1h in spectroscopic grade methanol and rinsewith absolute ethanol or isopropanol.

[0333] Glass slides with monolayer coatings of nanoparticles wereprocessed after cleaning as follows (hereafter referred as monolayeredslides):

[0334] a) Dipped for 10 min in a saturated isopropanol (reagent)solution of KOH, and then rinsed with DI water and dried using anitrogen flow.

[0335] b) A solution of 75 ml of toluene, 0.5 ml of isopropylamide and 2ml of 2-mercaptopropyltrimethylsiloxane was prepared and kept at 60° C.for an hour.

[0336] c) the slides were dipped in the solution for 1h at 60° C., andthen rinsed with hexane (spectrophotometric grade).

[0337] d) The samples were immersed overnight in hexane.

[0338] e) A CH₂Cl₂ solution (2 mg/ml of nanoparticle nAg6) was solventcasted by solvent evaporation on the slides

[0339] f) The samples were immersed overnight in hexane.

[0340] ITO (Indium Tin Oxide) slides were cleaned simply by rinsing themin ethanol on them.

[0341] Nanocomposite Film Casting by Solvent Evaporation

[0342] A fixture for hold samples for casting by solvent evaporation wasfabricated and used for all such castings this plate held substratesfixed in a horizontal position and allowed for control of theatmosphere. Under each slide 3 ml of reagent grade chloroform wereplaced prior to casting so to initially maintain the saturation of theatmosphere with solvent vapor upon introduction of the casting syrup.Each slide compartment was closed using a watch glass, so that thevolume of air in which each slide was casted was approx. 15 cm³.

[0343] Solvents were degassed by freeze-pump-thaw cycle.

Example 8

[0344] FI Standard 100 μm Film

[0345] 188.86 mg of polymer a₁ (poly 9-vinylcarbazole), 89.6 mg ofethylcarbazole, 2.59 mg of nAg6, and 8.77 mg of dye 1d were dissolved in6 ml of degassed chloroform under argon atmosphere and left stirringovernight.

[0346] On the following day 22 mg of AgBF₄ were dissolved in 0.02 ml ofdegassed acetonitrile and mixed to the chloroform solution. After 30 minthe solution was filtered with a membrane filter (1 μm pore size). 0.6ml of the filtered solution were casted on a 25×25 mm ITO slide.

Example 9

[0347] F2 Standard 100 μm Film

[0348] 660 mg of polymer a₁ (poly 9-vinylcarbazole), 329 mg ofethylcarbazole, 2.8 mg of nAg6, and 28 mg of dye 1d were dissolved in 6ml of degassed chloroform under argon atmosphere and left stirringovernight.

[0349] On the following day 110 mg of AgBF₄ were dissolved in 0.33 ml ofdegassed acetonitrile and 0.3 ml of those were added to the chloroformsolution. After 10 min the solution was filtered with a membrane filter(1 μm pore size). 2 ml of the filtered solution were casted on a 75×25mm glass slide.

Example 10

[0350] F3 20 μm Film With High Loading of Nanoparticles

[0351] 92 mg of polymer a₁ (poly 9-vinylcarbazole) were dissolved in 5ml of dichloromethane (DCM), 12 mg of AgBF₄ were dissolved in 5 ml ofDCM and 1 ml of acetonitrile, 5 mg of dye 1d were dissolved in 5 ml ofDCM, 5.5 mg of nAg1 were dissolved in 2 ml of chloroform. All solutionwere stirred for 2 h and then mixed together. 2 ml of the solution werecarted on a 75×25 mm glass slide.

Example 11

[0352] F4 Films for TEM

[0353] 11.5 mg of polymer a₁ (poly 9-vinylcarbazole), 2.4 mg of AgBF₄,2.8 mg of dye 1d, 1 mg of nAg1 were dissolved in 10 ml of DCM; solutionwas diluted 10 times and 2 μl of this solution were carted on a carboncoated copper grid. Three identical films were made in this way.

[0354]FIG. 9 shows TEM images illustrating growth of metal nanoparticlein a composite film upon exposure to either one or three laser pulsesfrom a ns pulsed laser. The upper TEM image shows the system after onelaser shot, the lower after three. In the upper limit the average radiushas become 4.9 nm, in the non-irradiate sample it was 2.9. In the lowerimage the average diameter is even bigger and larger metal islands canbe seen.

Example 12

[0355] FS Standard 100 μm Film With a Different Kind of Nanoparticle

[0356] 648 mg of polymer a₁ (poly 9-vinylcarbazole), 316 mg ofethylcarbazole, 2.75 mg of nAg7, and 20.7 mg of dye 1d were dissolved in6 ml of degassed chloroform under argon atmosphere and left stirringovernight.

[0357] On the following day 219 mg of AgBF₄ were dissolved in 0.6 ml ofdegassed acetonitrile and 0.2 ml were mixed to the chloroform solution.After 30 min the solution was filtered with a membrane filter (1 μm poresize). 0.4 ml of the filtered solution were carted on a 25×25 mm ITOslide.

Example 13

[0358] F6 Standard 10 μm Film

[0359] 64.5 mg of polymer a₁ holy 9-vinylcarbazole), 38.1 mg ofethylcarbazole, 1.21 mg of nAg6, and 3.31 mg of dye 1d were dissolved in6 ml of degassed chloroform under argon atmosphere and left stirringovernight.

[0360] On the following day 20.4 mg of AgBF₄ were dissolved in 0.3 ml ofdegassed acetonitrile and 0.1 ml were mixed to the chloroform solution.After 30 min the solution was filtered with a membrane filter (1 μmpores). 0.4 ml of the filtered solution were casted on a 75×25 mm glassslide.

Example 14

[0361] F7 Standard 100 μm Film With a Different Dye

[0362] 411.16 mg of polymer a₁ (poly 9-vinylcarbazole), 206.48 mg ofethylcarbazole, 2.28 mg of nAg6, and 19.72 mg of dye 2b were dissolvedin 6 ml of degassed chloroform under argon atmosphere and left stirringovernight.

[0363] On the following day 50.8 mg of AgBF₄ were dissolved in 0.3 ml ofdegassed acetonitrile and mixed to the chloroform solution. After 30 minthe solution was filtered with a membrane filter (1 μm pores). 0.6 ml ofthe filtered solution were casted on a 75×25 mm monolayered glass slide.

Example 15

[0364] F8 Standard 100 μm Film With a Different Polymer

[0365] 95.1 mg of polymer a₂ (PCUEMA), 0.71 mg of nAg6, and 1.8 mg ofdye 1d were dissolved in 1 ml of degassed chloroform under argonatmosphere and left stirring overnight.

[0366] On the following day 9.5 mg of AgBF₄ were dissolved in 0.05 ml ofdegassed acetonitrile and mixed to the chloroform solution. After 30 minthe solution was filtered with a membrane filter (1 μm pores). 0.6 ml ofthe filtered solution were casted on a 25×25 mm monolayered glass slide.

Example 16

[0367] F9 Standard 100 μm Film for Copper Generation

[0368] 66.6 mg of polymer a₄ (poly methylmethacrylate), 1.1 mg of nCu1,and 3.08 mg of dye 1d were dissolved in 0.6 ml of degassed chloroformunder argon atmosphere and left stirring overnight.

[0369] On the following day 5 mg of ICuP(CH₃)₃ were dissolved in 0.05 mlof degassed acetonitrile and mixed to the chloroform solution. After 30min the solution casted on a 25×25 mm glass slide

[0370] Spin Coated Films

Example 17

[0371] F10 Standard Spin Coated Film

[0372] 100 mg of polymer a₁ (poly 9-vinylcarbazole), 6 mg ofethylcarbazole, 3 mg of nAg4, and 4.5 mg of dye 1d were dissolved in 1ml of chloroform and left stirring overnight.

[0373] On the following day 100 mg of AgBF₄ were dissolved in 1 ml ofacetonitrile and 0.1 ml were added to the chloroform solution. After 30min the solution was spin coated on a 25×25 mm glass slide at 2000 RPMfor 20s. The obtained thickness was 8 μm, as proved by prism couplermeasurements.

[0374] Nanoparticle Containing Viscous Liquid

Example 18

[0375] F11 Standard Viscous Liquid Matrix Film

[0376] A quantity of host c₁ was heated using an heatgun and as soon asit flowed freely it was pipetted in a vial into order to weigh a fixedamount.

[0377] 226 mg of host c₁, 2 mg of nAg6, and 5.77 mg of dye 1d weredissolved in 2 ml of chloroform and left stirring overnight.

[0378] On the following day 11 mg of AgBF₄ were dissolved in 0.1 ml ofacetonitrile and mixed to the chloroform solution. After 30 min thesolution was casted on a 75×25 mm glass slide.

[0379] Class I Films

Example 19

[0380] F12 Standard Class I Film

[0381] 5.23 mg of nAg1, and 0.5 mg of dye 1d, and 0.5 mg of AgBF₄ weredissolved in 2 ml of chloroform left stirring overnight.

[0382] On the following day the solution was casted on a 75×25 mm glassslide.

[0383]FIG. 10 shows a silver ribbon written with a two-photonirradiation (800 nm, 120 fs) (Example 19).

[0384] Metal Writing in Nanoparticle Composites Using One and Two PhotonExcitation

[0385] All writing experiments were performed using a femtosecondmode-locked Ti:sapphire laser. Specifically a Spectra Physics systemconsisting of a Tsunami (Ti:sapphire laser) pumped by a Millenia (diodespumped YAG laser) was used. The average pulse length was 120 fs with abandwidth of ˜20 nm. Unless specified otherwise the wavelength used was760 nm.

[0386] The sample was mounted on a micropositioner (Sutter MP-285). Thelaser beam was focused on the sample using an inverted microscope(Nikon). A computer controlled both the micropositioner and a shutter(Newport 846HP). The combination of the micropositioner movements andthe opening/closing cycles of the shutter allowed patterned exposuresand metallic structures to be written in the sample.

[0387] In order to locate the focus of the beam in the sample atwo-photon microscopy setup was used, the beam was going through aBiorad MRC-1024 scanhead.

[0388] Writing Using Single Photon Excitation

[0389] In the case of writing using single photon excitation, the laseroutput light was frequency doubled double using a LBO doubling crystaland the remaining fundamental light left was filtered away using acombination of a crystal polarizer and an infrared short pass dielectricfilter.

[0390] The rest of the set-up was identical to the two-photon writingprocess, above described. The focusing process was done using thescanhead in a confocal fashion.

Example 20

[0391] Threshold Measurements for One-Photon Writing of Silver

[0392] Film F1 (Example 8) was mounted on the micropositioner, in thestandard way. The laser output wavelength was set at 860 nm (420 mW) andwas not changed during the experiment. A filter wheel was placed in theset up so to be able to make continuous and controllable variations inthe average power of the laser. The stage translation speed was set at10 μm/s. The beam was focused in the sample using a 60×objective (NA1.4). It was possible to write lines in the film everywhere and thebehavior was mostly uniform: so for a comparison with the two-photonexperiment the threshold was calculated at the glass/film interface. Thepower was gradually decreased and the success of the writing process wasdetermined by optical microscopy. The writing threshold was found to be0.09 mW. If we make the hypothesis of a circular beamspot with adiameter of 1 μm, we find a threshold intensity of approx. 10⁸ W/m² forthese 120 fs pulses.

[0393] For a pattern of lines written spaced of 5 μm we were able to putan upper limit to their width using the optical images, this limit being500 nm.

[0394]FIG. 11 shows silver lines written using a one-photon excitation(430 nm), lines are clearly visible. The dark spots are defects in thefilm which was not of optimal quality.

[0395] Writing Using Two-Photon Excitation.

[0396] Dye utilized herein as two-photon excitable photoreducing agentswere known to have a reasonably large two-photon cross-section thusallowing efficient two-photon excitation. This in combination with ahigh NA focusing system, allows writing high resolution lines inthree-dimensional patterns in the matrix.

Example 21

[0397] Threshold Measurements for Two-Photon Writing of Silver

[0398] Film F1 (Example 8) was mounted on the micropositioner, in thestandard way. The laser output wavelength was set at 760 nm (620 mW) andwas not changed during the experiment. A filter wheel was placed in theset up so to be able to make continuous and controllable variations inthe average power of the laser. The stage translation speed was set at10 μm/s. The beam was focused in the sample using a 60×objective (NA1.4). Lines were written everywhere in the film the behavior was mostlyuniform, so to have the possibility to further develop the structuresthe threshold was calculated at the glass/film interface. The power wasgradually decreased and the success of the writing process wasdetermined by optical microscopy. The writing threshold was found to be1.55 mW. If we make the hypothesis of a circular beamspot with adiameter of 1 μm, we find an intensity threshold of approx. 1.5 10⁹W/m².

[0399] For a pattern of lines written spaced of 5 μm we were able to putan upper limit to their width using the optical images, this limit being1 μm.

Example 22

[0400] Multiphoton Writing and Developing

[0401] Film F3 (Example 10) was mounted on the micropositioner, in thestandard way. The laser output wavelength was set at 800 nm (400 mW) andwas not changed during the experiment. The writing speed was set at 100μm/s. The microscope objective used was a 10×. Lines were written at theglass/film interface. A regular pattern of 6 sets of 5 lines each waswritten. Each set was places 30 μm away from the previous and the lineswere spaced 10 mm away to each other; all the lines were 500 μm long.After writing the film was placed in a DCM containing beaker and leftthere for 3 days. In doing these the polymer was washed away and thelines stayed on the substrate.

Example 23

[0402] Multiphoton Writing and Developing

[0403] Film F2 (Example 9) was mounted on the micropositioner, in thestandard way. The laser output wavelength was set at 760 nm (620 mW) andwas not changed during the experiment. The stage translation speed wasset at 10 μm/s. The beam was focused in the sample using a 60×objective(NA 1.4) and an immersion oil was used. Lines were written everywhere inthe film the behavior was mostly uniform. Many different patterns werewritten, the most significant one being a cage “like” structure with a13 layer of sets of lines each layer being 5 μm higher than theprevious, each layer consisting of 20 lines 100 μm long and spaced of 5μm, each layer consisting of lines perpendicular to the ones of theprevious layer.

[0404] After the writing process was done the film was removed from themicropositioner, cleaned from the immersion oil using a paper tissue andthen put in a solution of DCM and acetonitrile (10:1). The polymerdissolved away leaving the structure on the substrate.

[0405]FIG. 4 illustrates an optical transmission image, (top view) of a3D structure (200×200×65 μm) written in a polymer a₁ matrix. The writingprocess was done using a two-photon excitation (760 nm, 120 fs).

[0406]FIG. 5 illustrates an optical image of the same structure shown inFIG. 4 on a larger scale, the optical quality of the matrix is clearlyquite good.

[0407]FIG. 6 is a SEM image of a 3D metallic silver microstructureformed by two-photon writing in a composite film, they revealed bywashing to produce a free standing structure on the surface.

Example 24

[0408] Multiphoton Writing of Copper Structures

[0409] Film F9 (Example 16) was mounted on the micropositioner, in thestandard way. The laser output wavelength was set at 760 nm (620 mW) andwas not changed during the experiment. A square of copper was writtenusing the a 10×lens. The result was checked via optical imaging.

[0410]FIG. 12 shows an optical micrograph of a copper square (200×200μm) written by two-photon excitation.

Example 25

[0411] Control Experiment, F13

[0412] 10 mg of PVK where dissolved in 10 ml of dichloromethane, 1 mg ofAgBF₄ was dissolved in the same solution, 1 mg of dye 1 was then added.The solution was casted on a 75×25 mm glass slide.

[0413] The film was put in a UV chamber and irradiated at 419 nm with 15lamps (5W each). The optical absorption was followed and the results aresummarized in FIG. 13, just the bleaching of the nanoparticle band wasobserved.

[0414]FIG. 13 shows a spectrum of the sample from control experimentshowing the absence of formation of metal nanoparticle in a filmcontaining dyes and metal salt but no initial concentration of metalnanoparticle. Note the absence of the absorption band of metalnanoparticles following exposure. The solid line represent the spectrumof the film 13, the bands around 300 nm are due to the polymer itselfwhile the band at 426 is characteristic of dye 1. The dashed linerepresents the same film irradiated for 30 min while the dotted one for60 min.

[0415] Characterization

[0416] XPS

[0417] Metallic Silver lines written according to the proceduresdescribed above (Example 22) were analyzed using XPS spectroscopy andtheir Auger Parameter was measured to be 726.2 meV, perfectly matchingthe tabulated one for Ag⁰. Images of the written lines could be recordedusing the spectrometer in an imaging mode.

[0418]FIG. 7 shows a XPS spectrum (above) and image (below) a set ofsilver lines. The Auger parameter obtained from the spectrum is 726.2,which is the same as that tabulated one for zerovalent silver.

[0419] SEM

[0420] The structures were coated with a very thin metallic layer (Au/Iralloy) for SEM imaging. FIG. 14 shows an SEM picture of the corner of a3D metallic silver structure written using two-photon excitation. Themultiple layers written are evident.

[0421] TEM Characterization of Metal Nanoparticle Growth.

[0422] A nanosecond YAG laser (20 Hz) doubled light (532 nm) was used insingle shot fashion for the following experiment. One of the amorphouscarbon coated copper grid with the composite film on it (estimatedthickness 50 nm) was not used and left as a reference, the second onereceived a single laser pulse, the third one received three laserpulses. The average energy of each pulse was 120 μJ. The average radiusof the particle in the reference grid was found to be 2.95 nm; in thesecond grid it was 4.95 nm, in the third grid it was found to be approx.9.5 nm. Moreover the number of nanoparticle per unit area was found notto increase.

[0423]FIG. 15 shows a TEM image of chemically synthesized nanoparticles(nAg1) used as a precursor in the composites. A solution ofnanopartieles sample was sonicated for a minute in acetone and then onedrop of the solution was dried on a copper grid coated with amorphouscarbon. The microscope used was an Hitachi 8100.

[0424] Conductivity of Silver Lines

[0425] Tests were performed that demonstrated that the silver lines wereelectrically conductive. In one test, probes from a volt-ohm meter werecontacted to a written pad of silver and impedance of ˜80MΩ was measuredover a distance of 200 mm. Since good electrical contact was notassured, this gives an upper limit on the impedance of this length oftie line.

[0426] Exchange Reaction on nAg7 With Thiol Functionalized Dyes, GeneralProcedure:

[0427] The silver nanoparticles were dissolved in CH₂Cl₂ and stirred fortwo hour to ensure complete dissolution. The dye was added and the flaskcovered with aluminum foil. After stirring for 4 days the solvent wasremoved in vacuum with the moderate heating to a maximum of 35° C.Acetone was added and the precipitated nanoparticles collected onquantitative filter paper and washed with acetone until the solventshowed no sign of fluorescence in ultraviolet light. The nanoparticleswere dried in air and analyzed by elemental analysis.

Example 26

[0428] I₁₁ Functionalized Nanoparticles (nAg12):

[0429] Octylthiol/dodecylthiol protected silver nanoparticles (nAg7)(250 mg),4-((E)-2-{4-[(E)-2-(4-formylphenyl)ethenyl]-2-[(11-mercaptoundecyl)oxy]-5-methoxyphenyl}ethenyl)benzaldehyde(I₁₁) (14.1 mg, 0.025 mmol), CH₂Cl₂ (500 ml). Anal. (%) for nAg12(duplicated analysis): C: 11.78 (11.70), H: 2.07 (2.01), S: 2.76 (2.86),Ag: 76.62 (76.13).

Example 27

[0430] I₁₀ Functionalized Nanoparticles (nAg11):

[0431] Octylthiol/dodecylthiol protected silver nanoparticles (nAg7)(150 mg),11-(2,5-bis{(E)-2-[4-(diethylamino)phenyl]ethenyl}-4-methoxyphenoxy)undecan-1-thiol(I₁₀) (50 mg, 0.076 mmol), CH₂Cl₂ (300 ml). Isolated yield: 80.5 mg.Anal. (%) for nAg11 (duplicated analysis): C: 19.41 (19.45), H: 2.85(2.76), N: 0.62 (0.62), S: 3.06 (3.24), Ag: 71.10 (71.06).

Example 28

[0432] I₉ Functionalized Nanoparticles (nAg10):

[0433] Octylthiol/dodecylthiol protected silver nanoparticles (nAg7)(150 mg),11-{4-methoxy-2,5-bis[(E)-2-(4-nitrophenyl)ethenyl]phenoxy}-1-undecanethiol(I₉) (46 mg, 0.076 mmol), CH₂Cl₂ (300 ml). Anal. (%) for nAg10(duplicated analysis): C: 20.38 (20.40), H: 2.41 (2.26), N: 0.99 (0.96),S: 2.98 (2.86), Ag: 63.92 (63.97).

Example 29

[0434] I₉ Only Functionalized Nanoparticles (nAg13):

[0435] 116.5 mg of silver nitrate were dissolved in ˜75 ml ethanol at 0°C. 138 mg of I₉ were dissolved in a mixture of ˜100 ml acetone and 5 mlof dichloromethane. The dye solution was added to the silver nitratesolution and allowed to stir for 45 minutes. 75 ml of a saturated sodiumborohydride solution in ethanol were added dropwise over a four hoursperiod. The solution was allowed to stir for an additional three hours.The solution was stored in a refrigerator overnight and allowed todecant. The precipitate was filtered and washed with water, acetone, anddichloromethane. 146.3 mg of a black powder were collected. Anal. (%)for nAg13: C: 41.00, H: 4.10%, N: 2.88%, S: 3.57%, Ag: 37.51%.

[0436] Composition and Preparation of Films of Nanoparticles

Example 30

[0437] F14 Film of Dye Attached Nanoparticles Class (i), 20 nm Thick

[0438] 1 mg of nAg12 was dissolved in 20 cc of chloroform and left tostir for 2 days. 2 mg of AgBF₄ were dissolved in 10 cc of acetonitrile;0.1 cc of this solution were added to the nanoparticle solution. 0.5 ccof the combined solution was cast on a 25×25 mm ITO coated glass slides.

Example 31

[0439] F15 Film of Dye Attached Nanoparticles Class (ii), 20 nm Thick

[0440] 1 mg of nAg12 was dissolved in 20 cc of chloroform and left tostir for 2 days. The film was prepared casting 0.5 cc of the solution ona 25×25 mm ITO coated glass slides.

Example 32

[0441] F16 Film of Dye Attached Nanoparticles Class (iii), 20 nm Thick

[0442] 1 mg of nAg7 was dissolved in 20 cc of chloroform and left tostir for 2 days. 2 mg of AgBF₄ were dissolved in 10 cc of acetonitrile;0.1 cc of this solution were added to the nanoparticle solution. 0.5 ccof the combined solution was cast on a 25×25 mm ITO coated glass slides.

Example 33

[0443] F17 Film of Dye attached Nanoparticles Class (iv), 20 nm Thick

[0444] 1 mg of nAg7 was dissolved in 20 cc of chloroform and left tostir for 2 days. The film was prepared casting 0.5 cc of the solution ona 25×25 mm ITO coated glass slides.

Example 34

[0445] F18 Film of Dye Attached Nanoparticles Class (i), Submonolayer

[0446] 1 mg of nAg12 was dissolved in 20 cc of chloroform and left tostir for 2 days. 2 mg of AgBF₄ were dissolved in 10 cc of acetonitrile;0.1 cc of this solution were added to the nanoparticle solution. 2 cc ofthe combined solution were diluted 10 times with chloroform, and 2 μlwere deposited on a Si₃N₄ coated Si substrate (1 m²)

Example 35

[0447] F19 Film of Dye Attached Nanoparticles Class (ii), Submonolayer

[0448] 1 mg of nAg12 was dissolved in 20 cc of chloroform and left tostir for 2 days. 2 cc of the solution were diluted 10 times withchloroform, and 2 μl were deposited on a Si₃N₄ coated Si substrate (1mm²)

Example 36

[0449] F20 Film of Dye Attached Nanoparticles Class (iii), Submonolayer

[0450] 1 mg of nAg7 was dissolved in 20 cc of chloroform and left tostir for 2 days. 2 mg of AgBF₄ were dissolved in 10 cc of acetonitrile;0.1 cc of this solution were added to the nanoparticle solution. 2 cc ofthe combined solution were diluted 10 times with chloroform, and 2 μlwere deposited on a Si₃N₄ coated Si substrate (1 mm²).

Example 37

[0451] F21 Film of Dye Attached Nanoparticles Class (iv), Submonolayer

[0452] 1 mg of nAg7 was dissolved in 20 cc of chloroform and left tostir for 2 days. 2 cc of the solution were diluted 10 times withchloroform, and 2 μl were deposited on a Si₃N₄ coated Si substrate (1mm²).

Example 38

[0453] -F22 Polymer Based Film for Nanoparticle Growth

[0454] 1 mg of nAg12 was dissolved in 20 cc of chloroform and left tostir for 2 days. 200.6 mg of PVK and 89 mg of ethylcarbazole weredissolved in 2 cc of the nanoparticle solution and left to stir for 1day. 210 mg of AgBF₄ were dissolved in 1 cc of acetonitrile; 0.1 cc ofthis solution were added to the nanoparticle/polymer solution. The wholesolution was cast on a 25×75 mm glass slide.

Example 39

[0455] F23 Film for Reflectivity

[0456] 271 mg of PCUEMA, 20.5 mg of ethylcarbazole, 1.67 mg of nAg6, and7.16 mg of 1d were dissolved in 6 cc of chloroform and left to stirovernight. 27 mg of AgBF₄ were dissolved in 0.2 cc of acetonitrile andadded to the solution. The combined solution was filtered using a 1 μmpores filter and 2 cc of the filtered solution were cast on a 25×75 mmglass slide.

Example 40

[0457] F24 Film for Conductivity

[0458] 2 mg of nAg6 were dissolved in 5 cc of chloroform and left tostir for 1 day. The solution was filtered with a 1 mm pores filter. 21mg of PVK, 9 mg of ethylcarbazole, and 1.3 mg of 1d were dissolved in0.3 cc of the nanoparticles solution and left to stir for 2 hours. 20 mgof AgBF₄ were dissolved in 0.5 cc of acetonitrile, 0.05 cc of thissolution were added to the polymer nanoparticle solution. The solutionwas cast of half of a tailor made glass slide (25×25 mm), while theother half was covered with Teflon tape.

[0459] The slide had on it a pattern of 40 parallel silver lines 150 μmwide, 15 mm long and 50 nm height. The lines were spaced of 32 μm, andwere fabricated using standard e beam lithography techniques

Example 41

[0460] F25 Copper Microfabrication Film

[0461] The film was formed by dissolving 66 mg ofpoly(methylmethacrylate) PMMA, 1.1 mg of ligand coated coppernanoparticles nCu1, 5 mg of CuP(CH₃)₃I, and 3 mg of dye 1d in 0.6 ml ofdegassed CHCl₃ and cast on a 25×25 mm glass slide under an argonatmosphere.

Example 42

[0462] E26 Gold Microfabrication Film

[0463] The film was formed by dissolving 66 mg of PMMA, 1.1 mg of ligandcoated gold nanoparticles nAu1, 5 mg of AuP(CH₃)₃Br, and 3 mg of dye 1din 0.6 ml of CHCl₃ and cast on a 25×25 mm glass slide under an argonatmosphere.

Example 43

[0464] F27 Film for Holography

[0465] 271 mg of PVK, 20.5 mg of ethylcarbazole, 1.67 mg of nAg6, and0.8 mg of 1d were dissolved in 6 cc of chloroform and left to stirovernight. 27 mg of AgBF₄ were dissolved in 0.2 cc of acetonitrile andadded to the solution. The combined solution was filtered using a 1 μmpores filter and 2 cc of the filtered solution were cast on a 25×75 mmglass slide.

[0466] Provisional U.S. patent application 60/256,148, filed Dec. 15,2000, and the patents and literature references cited in the DetailedDescription, are incorporated herein by reference.

[0467] Obviously, numerous modifications and variations on the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

1. A method for growth of a pre-nucleated metal nanoparticle,comprising: providing said pre-nucleated metal nanoparticle in acomposite; generating a metal atom by reducing a metal ion by exposureto radiation; reacting said metal atom with said pre-nucleated metalnanoparticle, thereby growing a metal nanoparticle.
 2. The methodaccording to claim 1, further comprising collapsing of at least twometal nanoparticles, thereby obtaining a metallic continuous phase. 3.The method according to claim 1, wherein said metal atom is generatedfrom the metal ion by using an electron-beam.
 4. The method according toclaim 1, wherein said metal atom is generated by laser excitation of amolecule, thereby generating heat and causing thermal reduction of themetal ion.
 5. The method according to claim 1, wherein said metal atomis generated by photo-excitation of a molecule, thereby creating anexcited state of said molecule and increasing a reducing potential ofsaid molecule; and reducing of said metal ion by said molecule in saidexcited state to obtain the metal atom.
 6. A method for growth of apre-nucleated metal nanoparticle, comprising: forming a film from saidpre-nucleated metal nanoparticle, a metal salt, a dye and a polymermatrix; generating a metal atom by reducing a metal ion of said metalsalt by exposure to radiation; reacting said metal atom with saidpre-nucleated metal nanoparticle, thereby growing a metal nanoparticle.7. A metal nanoparticle containing composition, comprising: a ligandcoated metal nanoparticle; a dye; a metal salt; and optionally asacrificial donor.
 8. The composition according to claim 7, wherein saiddye is capable of reducing a metal ion from said metal salt underexposure to radiation.
 9. The composition according to claim 7, whereinsaid metal nanoparticle is selected from the group consisting of ananoparticle of a metal coated with an organic ligand, a nanoparticle ofan alloy of metals coated with an organic ligand, and a metallicnanoshell nanoparticle coated with an organic ligand.
 10. Thecomposition according to claim 9, wherein a core of said metallicnanoshell nanoparticle is selected from the group consisting of asemiconductor nanoparticle, a metal oxide nanoparticle, a SiO_(x)nanoparticle, a polymer nanoparticle and a protein nanoparticle; andwherein an outer shell of said metallic nanoshell is metallic and coatedwith an organic ligand coating.
 11. The composition according to claim7, wherein said metal nanoparticle is stabilized by an organic ligand ora mixture of organic ligands.
 12. The composition according to claim 11,wherein said organic ligand is a molecule of formula A-B-C.
 13. Thecomposition according to claim 12, wherein A is a molecular or ionicfragment that has at least one atom having a lone pair of electrons thatcan bond to a metal nanoparticle surface, or is an unsaturated molecularor ionic fragment that can bond to the metal nanoparticle surface, andincludes a point of attachment to connect the fragment to B.
 14. Thecomposition according to claim 12, wherein A and C are eachindependently selected from the group consisting of ^(e)S, ^(e)O—,^(e)O₂C—, ^(e)S—S—R, ^(e)O₃S—, ^(e)S₂C—NR—, ^(e)O₂C—NR—, P(R₁R₂)—,N(R₁R₂)—, O(R₁)—, P(OR₁)(OR₂)O—, and S₂(R)—; wherein R, R₁, and R₂ maybe independently selected from the group consisting of —H, a linear orbranched alkyl chain containing 1 to 50 carbon atoms, a phenyl group, anaryl group other than a phenyl group, and a hetero aromatic group;wherein each of A and C independently has one point of attachment to B.15. The composition according to claim 12, wherein B is an organicfragment that has two points of attachment, one for connecting to part Aand one for connecting to part C.
 16. The composition according to claim12, wherein B is a single bond.
 17. The composition according to claim12, wherein B and C are each independently selected from the groupconsisting of a methylene chain with 1 to 50 carbon atoms, a phenylenechain with 1 to 20 phenyls, a thiophenylene chain with 1 to 20thiophenylenes, a phenylene vinylene chain with 1 to 20 phenylvinylenes, a branched hydrocarbon chain, an ethylene oxide chain with 1to 20 ethylene oxides, an oligo (vinyl carbazole) chain with 1 to 20vinyl carbazole units; wherein B has two points of attachment; andwherein C has one point of attachment.
 18. The composition according toclaim 12, wherein C is a molecular fragment with one point of attachmentthat connects to fragment B.
 19. The composition according to claim 18,wherein C is selected from the group consisting of —H, an aryl group,N-carbazoyl, α-fluorenyl, —SiOR₃, —SiCl₃, a dye, a donor-acceptor dye, aphotoreducing dye, a multi-photon absorbing chromophore, methylene blue,an oligonucleotide strand, a peptide chain.
 20. The compositionaccording to claim 18, wherein C is selected from the group consistingof a carbazole, a bis-styrylbenzene, a cyanine and a thiophene.
 21. Thecomposition according to claim 18, wherein said ligand A-B-C is selectedfrom the group consisting of octanethiol, dodecanthiol, heptanethiol,8-(9H-carbazol-9-yl)octane-1-thiol,8-(9H-carbazol-9-yl)dodecane-1-thiol, 3-mercaptopropionic acid,Bis[2-(dimethylamino)ethyl]2-mercaptopentadioate,3{2,5-bis[(E)-2-(4-formyl-(phenyl)ethenyl]phenoxy}propyl-4-(1,2-dithiolane-3-yl)butanoateand a mixture thereof.
 22. The composition according to claim 7, whereinsaid dye is attached to said metal nanoparticle.
 23. The compositionaccording to claim 7, wherein said dye is selected from the groupconsisting of a centrosymmetric bisaldehyde-bistyrylbenzene, anon-centrosymmetric bisaldehyde-bistyrylbenzene, a centrosymmetricacceptor terminated bistyrylbenzene, a non-centrosymmetric acceptorterminated bistyrylbenzene and a mixture thereof.
 24. A metalnanoparticle containing composition, comprising: a ligand coated metalnanoparticle; a dye; a metal salt; and a matrix.
 25. The compositionaccording to claim 24, wherein said matrix is selected from the groupconsisting of a polymer, a glass, a liquid crystalline material, aliquid and a porous crystalline solid.
 26. The composition according toclaim 24, wherein said matrix is a polymer selected from the groupconsisting of polyvinylcarbazole,poly(2-{[11-(9H-carbazole-9-yl)undecanoyl]oxy}ethyl-2-methacrylate),poly(p-chlorostyrene), poly(methylmethacrylate) and a mixture thereof.27. The composition according to claim 24, wherein said matrix is1-[11-(9H-carbazole-9-yl)]-4-methoxybenzene,1-[11-(9H-carbazole-9-yl)]-4-methylbenzene or a mixture thereof.
 28. Thecomposition of claim 24, further comprising a plasticizer.
 29. Thecomposition according to claim 28, wherein said plasticizer isN-ethylcarbazole, p,p′-formyl-N-octyl-carbazole or a mixture thereof.30. The composition according to claim 24, wherein said dye is capableof reducing a metal ion from said metal salt under exposure toradiation.
 31. The composition according to claim 24, wherein said metalnanoparticle is selected from the group consisting of a nanoparticle ofa metal coated with an organic ligand, a nanoparticle of an alloy ofmetals coated with an organic ligand, and a metallic nanoshellnanoparticle coated with an organic ligand.
 32. The compositionaccording to claim 24, wherein a core of said metallic nanoshellnanoparticle is selected from the group consisting of a semiconductornanoparticle, a metal oxide nanoparticle, a SiO_(x) nanoparticle, apolymer nanoparticle and a protein nanoparticle; and wherein an outershell of said metallic nanoshell is metallic and coated with an organiccoating.
 33. The composition according to claim 24, wherein said metalnanoparticle is stabilized by an organic ligand or a mixture of organicligands.
 34. The composition according to claim 33, wherein said organicligand is a molecule of formula A-B-C.
 35. The composition according toclaim 34, wherein A is a molecular or ionic fragment that has at leastone atom having a lone pair of electrons that can bond to a metalnanoparticle surface, or is an unsaturated molecular or ionic fragmentthat can bond to the metal nanoparticle surface, and includes a point ofattachment to connect the fragment to B.
 36. The composition accordingto claim 34, wherein A and C are each independently selected from thegroup consisting of ^(e)S, ^(e)O, ^(e)O₂C—, ^(e)S—S—R, ^(e)O₃S—,^(e)S₂C—NR—, ^(e)O₂C—NR—, P(R₁R₂)—, N(R₁R₂)—, O(R₁)—, P(OR₁)(OR₂)O—, andS₂(R)—; wherein R, R₁, and R₂ may be independently selected from thegroup consisting of —H, a linear or branched alkyl chain containing 1 to50 carbon atoms, a phenyl group, an aryl group other than a phenylgroup, and a hetero aromatic group; wherein each of A and Cindependently has one point of attachment to B.
 37. The compositionaccording to claim 34, wherein B is an organic fragment that has twopoints of attachment, one for connecting to part A and one forconnecting to part C.
 38. The composition according to claim 34, whereinB is a single bond.
 39. The composition according to claim 34, wherein Band C are each independently selected from the group consisting of amethylene chain with 1 to 50 carbon atoms, a phenylene chain with 1 to20 phenyls, a thiophenylene chain with 1 to 20 thiophenylenes, aphenylene vinylene chain with 1 to 20 phenyl vinylenes, a branchedhydrocarbon chain, an ethylene oxide chain with 1 to 20 ethylene oxides,an oligo (vinyl carbazole) chain with 1 to 20 vinyl carbazole units;wherein B has two points of attachment; and wherein C has one point ofattachment.
 40. The composition according to claim 34, wherein C is amolecular fragment with one point of attachment that connects tofragment B.
 41. The composition according to claim 40, wherein C isselected from the group consisting of —H, an aryl group, N-carbazoyl,α-fluorenyl, —SiOR₃, —SiCl₃, a dye, a donor-acceptor dye, aphotoreducing dye, a multi-photon absorbing chromophore, methylene blue,an oligonucleotide strand, a peptide chain.
 42. The compositionaccording to claim 40, wherein C is selected from the group consistingof a carbazole, a bis-styrylbenzene, a cyanine and a thiophene.
 43. Thecomposition according to claim 40, wherein said ligand A-B-C is selectedfrom the group consisting of octanethiol, dodecanthiol, heptanethiol,8-(9H-carbazol-9-yl)octane-1-thiol,8-(9H-carbazol-9-yl)dodecane-1-thiol, 3-mercaptopropionic acid,Bis[2-(dimethylamino)ethyl]2-mercaptopentadioate,3{2,5-bis[(E)-2-(4-formyl-(phenyl)ethenyl]phenoxy}propyl-4-(1,2-dithiolane-3-yl)butanoateand a mixture thereof.
 44. The composition according to claim 24,wherein said dye is attached to said metal nanoparticle.
 45. Thecomposition according to claim 24, wherein said dye is selected from thegroup consisting of a centrosymmetric bisaldehyde-bistyrylbenzene, anon-centrosymmetric bisaldehyde-bistyrylbenzene, a centrosymmetricacceptor terminated bistyrylbenzene, a non-centrosymmetric acceptorterminated bistyrylbenzene and a mixture thereof.
 46. A method,comprising: subjecting said metal nanoparticles containing compositionof claim 7 to radiation, thereby effecting a growth of saidnanoparticles; and forming a continuous or semi-continuous metal phase.47. A method, comprising: subjecting said metal nanoparticles containingcomposition of claim 24 to radiation, thereby effecting a growth of saidnanoparticles; and forming a continuous or semi-continuous metal phase.48. The method according to claim 47, wherein said nanoparticle is asilver nanoparticle with a mixture of ligands having the formula A-B-C.49. The method according to claim 48, wherein A is a molecular or ionicfragment that has at least one atom having a lone pair of electrons thatcan bond to a metal nanoparticle surface, or is an unsaturated molecularor ionic fragment that can bond to the metal nanoparticle surface, andincludes a point of attachment to connect the fragment to B.
 50. Themethod according to claim 48, wherein A and C are each independentlyselected from the group consisting of ^(e)S, ^(e)O, ^(e)O₂C—, ^(e)S—S—R,^(e)O₃S—, ^(e)S₂C—NR—, ^(e)O₂C—NR—, P(R₁R₂)—, N(R₁R₂)—, O(R₁)—,P(OR₁)(OR₂)O—, and S₂(R)—; wherein R, R₁, and R₂ may be independentlyselected from the group consisting of —H, a linear or branched alkylchain containing 1 to 50 carbon atoms, a phenyl group, an aryl groupother than a phenyl group, and a hetero aromatic group; wherein each ofA and C independently has one point of attachment to B.
 51. The methodaccording to claim 48, wherein B is an organic fragment that has twopoints of attachment, one for connecting to part A and one forconnecting to part C.
 52. The method according to claim 48, wherein B isa single bond.
 53. The method according to claim 48, wherein B and C areeach independently selected from the group consisting of a methylenechain with 1 to 50 carbon atoms, a phenylene chain with 1 to 20 phenyls,a thiophenylene chain with 1 to 20 thiophenylenes, a phenylene vinylenechain with 1 to 20 phenyl vinylenes, a branched hydrocarbon chain, anethylene oxide chain with 1 to 20 ethylene oxides, an oligo (vinylcarbazole) chain with 1 to 20 vinyl carbazole units; wherein B has twopoints of attachment; and wherein C has one point of attachment.
 54. Themethod according to claim 48, wherein C is a molecular fragment with onepoint of attachment that connects to fragment B.
 55. The methodaccording to claim 54, wherein C is selected from the group consistingof —H, an aryl group, N-carbazoyl, α-fluorenyl, —SiOR₃, —SiCl₃, a dye, adonor-acceptor dye, a photoreducing dye, a multi-photon absorbingchromophore, methylene blue, an oligonucleotide strand, a peptide chain.56. The method according to claim 54, wherein C is selected from thegroup consisting of a carbazole, a bis-styrylbenzene, a cyanine and athiophene.
 57. The method according to claim 54, wherein said ligandA-B-C is selected from the group consisting of octanethiol,dodecanthiol, heptanethiol, 8-(9H-carbazol-9-yl)octane-1-thiol,8-(9H-carbazol-9-yl)dodecane-1-thiol, 3-mercaptopropionic acid,Bis[2-(dimethylamino)ethyl]2-mercaptopentadioate,3{2,5-bis[(E)-2-(4-formyl-(phenyl)etheny]phenoxy}propyl-4-(1,2-dithiolane-3-yl)butanoateand a mixture thereof.
 58. The method according to claim 47, whereinsaid metal salt is AgBF₄.
 59. The method according to claim 47, whereinsaid dye is a multi-photon absorbing dye.
 60. A method, comprising:forming a film from a metal nanoparticle, a metal salt, a dye and apolymer matrix; and exposing said film to radiation, thereby producing apattern of a conductive metal.
 61. The method according to claim 60,wherein said nanoparticle is a silver nanoparticle with a mixture ofligands having the formula A-B-C.
 62. The method according to claim 61,wherein A is a molecular or ionic fragment that has at least one atomhaving a lone pair of electrons that can bond to a metal nanoparticlesurface, or is an unsaturated molecular or ionic fragment that can bondto the metal nanoparticle surface, and includes a point of attachment toconnect the fragment to B.
 63. The method according to claim 61, whereinA and C are each independently selected from the group consisting of^(e)S, ^(e)O—, ^(e)O₂C—, ^(e)—S—R, ^(e)O₃S—, ^(e)S₂C—NR—, ^(e)O₂C-NR—,P(R₁R₂)—, N(R₁R₂)—, O(R₁)—, P(OR₁)(OR₂)O—, and S₂(R)—; wherein R, R₁,and R₂ may be independently selected from the group consisting of —H, alinear or branched alkyl chain containing 1 to 50 carbon atoms, a phenylgroup, an aryl group other than a phenyl group, and a hetero aromaticgroup; wherein each of A and C independently has one point of attachmentto B.
 64. The method according to claim 61, wherein B is an organicfragment that has two points of attachment, one for connecting to part Aand one for connecting to part C.
 65. The method according to claim 61,wherein B is a single bond.
 66. The method according to claim 61,wherein B and C are each independently selected from the groupconsisting of a methylene chain with 1 to 50 carbon atoms, a phenylenechain with 1 to 20 phenyls, a thiophenylene chain with 1 to 20thiophenylenes, a phenylene vinylene chain with 1 to 20 phenylvinylenes, a branched hydrocarbon chain, an ethylene oxide chain with 1to 20 ethylene oxides, an oligo (vinyl carbazole) chain with 1 to 20vinyl carbazole units; wherein B has two points of attachment; andwherein C has one point of attachment.
 67. The method according to claim61, wherein C is a molecular fragment with one point of attachment thatconnects to fragment B.
 68. The method according to claim 67, wherein Cis selected from the group consisting of —H, an aryl group, N-carbazoyl,α-fluorenyl, —SiOR₃, —SiCl₃, a dye, a donor-acceptor dye, aphotoreducing dye, a multi-photon absorbing chromophore, methylene blue,an oligonucleotide strand, a peptide chain.
 69. The method according toclaim 67, wherein C is selected from the group consisting of acarbazole, a bis-styrylbenzene, a cyanine and a thiophene.
 70. Themethod according to claim 67, wherein said ligand A-B-C is selected fromthe group consisting of octanethiol, dodecanthiol, heptanethiol,8-(9H-carbazol-9-yl)octane-1-thiol,8-(9H-carbazol-9-yl)dodecane-1-thiol, 3-mercaptopropionic acid,Bis[2-(dimethylamino)ethyl]2-mercaptopentadioate,3{2,5-bis[(E)-2-(4-formyl-(phenyl)ethenyl]phenoxy}propyl-4(1,2-dithiolane-3-yl)butanoateand a mixture thereof.
 71. The method according to claim 60, whereinsaid metal salt is AgBF₄.
 72. The method according to claim 60, whereinsaid dye is a multi-photon absorbing dye.
 73. The method according toclaim 72, wherein a two-photon cross section is in excess of 1×10⁻⁵⁰ cm⁴photon⁻¹ sec⁻¹.